Hybrid maize plant and seed 31G20

ABSTRACT

According to the invention, there is provided a hybrid maize plant, designated as 31G20, produced by crossing two Pioneer Hi-Bred International, Inc. proprietary inbred maize lines. This invention relates to the hybrid seed 31G20, the hybrid plant produced from the seed, and variants, mutants, and trivial modifications of hybrid 31G20.

FIELD OF THE INVENTION

This invention is in the field of maize breeding, specifically relating to hybrid maize designated 31G20.

BACKGROUND OF THE INVENTION Plant Breeding

Field crops are bred through techniques that take advantage of the plant's method of pollination. A plant is self-pollinated if pollen from one flower is transferred to the same or another flower of the same plant. A plant is cross-pollinated if the pollen comes from a flower on a different plant.

Plants that have been self-pollinated and selected for type for many generations become homozygous at almost all gene loci and produce a uniform population of true breeding progeny. A cross between two different homozygous lines produces a uniform population of hybrid plants that may be heterozygous for many gene loci. A cross of two plants each heterozygous at a number of gene loci will produce a population of hybrid plants that differ genetically and will not be uniform.

Maize (Zea mays L.), often referred to as corn in the United States, can be bred by both self-pollination and cross-pollination techniques. Maize has separate male and female flowers on the same plant, located on the tassel and the ear, respectively. Natural pollination occurs in maize when wind blows pollen from the tassels to the silks that protrude from the tops of the ears.

The development of a hybrid maize variety involves three steps: (1) the selection of plants from various germplasm pools for initial breeding crosses; (2) the selfing of the selected plants from the breeding crosses for several generations to produce a series of inbred lines, which, although different from each other, breed true and are highly uniform; and (3) crossing the selected inbred lines with unrelated inbred lines to produce the hybrid progeny (F1). During the inbreeding process in maize, the vigor of the lines decreases. Vigor is restored when two different inbred lines are crossed to produce the hybrid progeny (F1). An important consequence of the homozygosity and homogeneity of the inbred lines is that the hybrid created by crossing a defined pair of inbreds will always be the same. Once the inbreds that create a superior hybrid have been identified, a continual supply of the hybrid seed can be produced using these inbred parents and the hybrid corn plants can then be generated from this hybrid seed supply.

Large scale commercial maize hybrid production, as it is practiced today, requires the use of some form of male sterility system which controls or inactivates male fertility. A reliable method of controlling male fertility in plants also offers the opportunity for improved plant breeding. This is especially true for development of maize hybrids, which relies upon some sort of male sterility system. There are several options for controlling male fertility available to breeders, such as: manual or mechanical emasculation (or detasseling), cytoplasmic male sterility, genetic male sterility, gametocides and the like.

Hybrid maize seed is typically produced by a male sterility system incorporating manual or mechanical detasseling. Alternate strips of two inbred varieties of maize are planted in a field, and the pollen-bearing tassels are removed from one of the inbreds (female) prior to pollen shed. Providing that there is sufficient isolation from sources of foreign maize pollen, the ears of the detasseled inbred will be fertilized only from the other inbred (male), and the resulting seed is therefore hybrid and will form hybrid plants.

The laborious, and occasionally unreliable, detasseling process can be avoided by using cytoplasmic male-sterile (CMS) inbreds. Plants of a CMS inbred are male sterile as a result of factors resulting from the cytoplasmic, as opposed to the nuclear, genome. Thus, this characteristic is inherited exclusively through the female parent in maize plants, since only the female provides cytoplasm to the fertilized seed. CMS plants are fertilized with pollen from another inbred that is not male-sterile. Pollen from the second inbred may or may not contribute genes that make the hybrid plants male-fertile. Usually seed from detasseled fertile maize and CMS produced seed of the same hybrid are blended to insure that adequate pollen loads are available for fertilization when the hybrid plants are grown.

There are several methods of conferring genetic male sterility available, such as multiple mutant genes at separate locations within the genome that confer male sterility, as disclosed in U.S. Pat. Nos. 4,654,465 and 4,727,219 to Brar et al. and chromosomal translocations as described by Patterson in U.S. Pat. Nos. 3,861,709 and 3,710,511. These and all patents referred to are incorporated by reference. In addition to these methods, Albertsen et al., of Pioneer Hi-Bred, U.S. patent application Ser. No. 07/848,433, have developed a system of nuclear male sterility which includes: identifying a gene which is critical to male fertility; silencing this native gene which is critical to male fertility; removing the native promoter from the essential male fertility gene and replacing it with an inducible promoter; inserting this genetically engineered gene back into the plant; and thus creating a plant that is male sterile because the inducible promoter is not "on" resulting in the male fertility gene not being transcribed. Fertility is restored by inducing, or turning "on", the promoter, which in turn allows the gene that confers male fertility to be transcribed.

There are many other methods of conferring genetic male sterility in the art, each with its own benefits and drawbacks. These methods use a variety of approaches such as delivering into the plant a gene encoding a cytotoxic substance associated with a male tissue specific promoter or an antisense system in which a gene critical to fertility is identified and an antisense to that gene is inserted in the plant (see: Fabinjanski, et al. EPO 89/3010153.8 publication no. 329,308 and PCT application PCT/CA90/00037 published as WO 90/08828).

Another system useful in controlling male sterility makes use of gametocides. Gametocides are not a genetic system, but rather a topical application of chemicals. These chemicals affect cells that are critical to male fertility. The application of these chemicals affects fertility in the plants only for the growing season in which the gametocide is applied (see Carlson, Glenn R., U.S. Pat. No. 4,936,904). Application of the gametocide, timing of the application and genotype specificity often limit the usefulness of the approach.

The use of male sterile inbreds is but one factor in the production of maize hybrids. The development of maize hybrids requires, in general, the development of homozygous inbred lines, the crossing of these lines, and the evaluation of the crosses. Breeding programs combine the genetic backgrounds from two or more inbred lines or various other broad-based sources into breeding pools from which new inbred lines are developed by selfing and selection of desired phenotypes. Hybrids also are used as starting materials for breeding or source populations from which to develop inbred lines. The inbred lines derived from hybrids can be developed using methods of breeding known in the art such as pedigree breeding and recurrent selection. New inbreds are crossed with other inbred lines and the hybrids from these crosses are evaluated to determine which of those have commercial potential.

Recurrent selection breeding, backcrossing for example, can be used to improve inbred lines and a hybrid which is made using those inbreds. Backcrossing can be used to transfer a specific desirable trait from one inbred or source to an inbred that lacks that trait. This can be accomplished, for example, by first crossing a superior inbred (recurrent parent) to a donor inbred (non-recurrent parent), that carries the appropriate gene(s) for the trait in question. The progeny of this cross is then mated back to the superior recurrent parent followed by selection in the resultant progeny for the desired trait to be transferred from the non-recurrent parent. After five or more backcross generations with selection for the desired trait and for the germplasm inherited from the recurrent parent, the progeny will be homozygous for loci controlling the characteristic being transferred, but will be like the superior parent for essentially all other genes. The last backcross generation is then selfed to give pure breeding progeny for the gene(s) being transferred. A hybrid developed from inbreds containing the transferred gene(s) is essentially the same as a hybrid developed from the same inbreds without the transferred gene(s).

There are many important factors to be considered in the art of plant breeding, such as the ability to recognize important morphological and physiological characteristics, the ability to design evaluation techniques for genotypic and phenotypic traits of interest, and the ability to search out and exploit the genes for the desired traits in new or improved combinations.

The objective of commercial maize hybrid line development programs is to develop new inbred lines to produce hybrids that combine to produce high grain yields and superior agronomic performance. The primary trait breeders seek is yield. However, many other major agronomic traits are of importance in hybrid combination and have an impact on yield or otherwise provide superior performance in hybrid combinations. Such traits include percent grain moisture at harvest, relative maturity, resistance to stalk breakage, resistance to root lodging, grain quality, and disease and insect resistance. In addition, the lines per se must have acceptable performance for parental traits such as seed yields, kernel sizes, pollen production, all of which affect ability to provide parental lines in sufficient quantity and quality for hybridization. These traits have been shown to be under genetic control and many if not all of the traits are affected by multiple genes.

Pedigree Breeding

The pedigree method of breeding is the mostly widely used methodology for new hybrid line development.

In general terms this procedure consists of crossing two inbred lines to produce the non-segregating F1 generation, and self pollination of the F1 generation to produce the F2 generation that segregates for all factors for which the inbred parents differ. An example of this process is set forth below. Variations of this generalized pedigree method are used, but all these variations produce a segregating generation which contains a range of variation for the traits of interest.

EXAMPLE 1 Hypothetical Example of Pedigree Breeding Program

Consider a cross between two inbred lines that differ for alleles at six loci. The parental genotypes are:

    ______________________________________                                         Parent 1         A b C d e F/A b C d e F                                       Parent 2         a B c D E f/a B c D E f                                       ______________________________________                                    

the F1 from a cross between these two parents is:

    ______________________________________                                         F1              A b C d e F/a B c D E f                                        ______________________________________                                    

Selfing F1 will produce an F2 generation including the following genotypes:

A B c D E f/a b C d e F

A B c D e f/a b C d E F

A B c D e f/a b C d e F

The number of genotypes in the F2 is 36 for six segregating loci (729) and will produce (26)-2 possible new inbreds, (62 for six segregating loci).

Each inbred parent which is used in breeding crosses represents a unique combination of genes, and the combined effects of the genes define the performance of the inbred and its performance in hybrid combination. There is published evidence (Smith, O. S., J. S. C. Smith, S. L. Bowen, R. A. Tenborg and S. J. Wall, TAG 80:833-840 (1990)) that each of the lines are different and can be uniquely identified on the basis of genetically-controlled molecular markers.

It has been shown (Hallauer, Arnel R. and Miranda, J. B. Fo. Quantitative Genetics in Maize Breeding, Iowa State University Press, Ames Iowa, 1981) that most traits of economic value in maize are under the genetic control of multiple genetic loci, and that there are a large number of unique combinations of these genes present in elite maize germplasm. If not, genetic progress using elite inbred lines would no longer be possible. Studies by Duvick and Russell (Duvick, D. N., Maydica 37:69-79, (1992); Russell, W. A., Maydica XXIX:375-390 (1983)) have shown that over the last 50 years the rate of genetic progress in commercial hybrids has been between one and two percent per year.

The number of genes affecting the trait of primary economic importance in maize, grain yield, has been estimated to be in the range of 10-1000. Inbred lines which are used as parents for breeding crosses differ in the number and combination of these genes. These factors make the plant breeder's task more difficult. Compounding this is evidence that no one line contains the favorable allele at all loci, and that different alleles have different economic values depending on the genetic background and field environment in which the hybrid is grown. Fifty years of breeding experience suggests that there are many genes affecting grain yield and each of these has a relatively small effect on this trait. The effects are small compared to breeders' ability to measure grain yield differences in evaluation trials. Therefore, the parents of the breeding cross must differ at several of these loci so that the genetic differences in the progeny will be large enough that breeders can develop a line that increases the economic worth of its hybrids over that of hybrids made with either parent.

If the number of loci segregating in a cross between two inbred lines is n, the number of unique genotypes in the F2 generation is 3n and the number of unique inbred lines from this cross is {(2n)-2}. Only a very limited number of these combinations are useful. Only about 1 in 10,000 of the progeny from F2's are commercially useful.

By way of example, if it is assumed that the number of segregating loci in F2 is somewhere between 20 and 50, and that each parent is fixed for half the favorable alleles, it is then possible to calculate the approximate probabilities of finding an inbred that has the favorable allele at {(n/2)+m} loci, where n/2 is the number of favorable alleles in each of the parents and m is the number of additional favorable alleles in the new inbred. See Example 2 below. The number m is assumed to be greater than three because each allele has so small an effect that evaluation techniques are not sensitive enough to detect differences due to three or less favorable alleles. The probabilities in Example 2 are on the order of 10-5 or smaller and they are the probabilities that at least one genotype with (n/2)=m favorable alleles will exist.

To put this in perspective, the number of plants grown on 60 million acres (approximate United States corn acreage) at 25,000 plants/acre is 1.5×1012.

EXAMPLE 2 Probability of Finding an Inbred With m of n Favorable Alleles

Assume each parent has n/2 of the favorable alleles and only 1/2 of the combinations of economically useful.

    ______________________________________                                          No. of  No. of favorable                                                                           No. additional                                            segregating                                                                             alleles in Parents                                                                         favorable alleles                                                                          Probability that                              loci (n)           (n/2)                                                                                            genotype occurs*                          ______________________________________                                             20    10          14          3 × 10-5                               24                                    2 × 10-5                           28                                    1 × 10-5                           32                                    8 × 10-6                           36                                    5 × 10-6                           40                                    3 × 10-6                           44                                    2 × 10-6                           48                                    l × 10-6                           ______________________________________                                          *Probability that a useful combination exists, does not include the            probability of identifying this combination if it does exist.            

The possibility of having a usably high probability of being able to identify this genotype based on replicated field testing would be most likely smaller than this, and is a function of how large a population of genotypes is tested and how testing resources are allocated in the testing program.

SUMMARY OF THE INVENTION

According to the invention, there is provided a hybrid maize plant, designated as 31G20, produced by crossing two Pioneer Hi-Bred International, Inc. proprietary inbred maize lines. This invention thus relates to the hybrid seed 31G20, the hybrid plant produced from the seed, and variants, mutants and trivial modifications of hybrid 31G20. This invention also relates to methods for producing a maize plant containing in its genetic material one or more transgenes and to the transgenic maize plants produced by that method. This invention further relates to methods for producing maize lines derived from hybrid maize line 31G20 and to the maize lines derived by the use of those methods. This hybrid maize plant is characterized by consistent high yield for its maturity and excellent staygreen. 31G20 has very strong stalks and good Northern Leaf Blight Resistance.

DEFINITIONS

In the description and examples that follow, a number of terms are used herein. In order to provide a clear and consistent understanding of the specification and claims, including the scope to be given such terms, the following definitions are provided. NOTE: ABS is in absolute terms and %MN is percent of the mean for the experiments in which the inbred or hybrid was grown. These designators will follow the descriptors to denote how the values are to be interpreted. Below are the descriptors used in the data tables included herein.

ADF=PERCENT ACID DETERGENT FIBER. This is the percent dry matter that is acid detergent fiber in chopped whole plant forage, which is a measure of fiber content.

ANT ROT=ANTHRACNOSE STALK ROT (Colletotrichum graminicola). A 1 to 9 visual rating indicating the resistance to Anthracnose Stalk Rot. A higher score indicates a higher resistance.

BAR PLT=BARREN PLANTS. The percent of plants per plot that were not barren (lack ears).

BRT STK=BRITTLE STALKS. This is a measure of the stalk breakage near the time of pollination, and is an indication of whether a hybrid or inbred would snap or break near the time of flowering under severe winds. Data are presented as percentage of plants that did not snap in paired comparisons and on a 1 to 9 scale (9=highest resistance) in Characteristics Charts.

BU ACR=YIELD (BUSHELS/ACRE). Yield of the grain at harvest in bushels per acre adjusted to 15.5% moisture.

CLN=CORN LETHAL NECROSIS (synergistic interaction of maize chlorotic mottle virus (MCMV) in combination with either maize dwarf mosaic virus (MDMV-A or MDMV-B) or wheat streak mosaic virus (WSMV)). A 1 to 9 visual rating indicating the resistance to Corn Lethal Necrosis. A higher score indicates a higher resistance.

COM RST=COMMON RUST (Puccinia sorghi). A 1 to 9 visual rating indicating the resistance to Common Rust. A higher score indicates a higher resistance.

CP=PERCENT OF CRUDE PROTEIN. This is the percent of dry matter that is crude protein in chopped whole plant forage.

CRM=COMPARATIVE RELATIVE MATURITY (see PRM).

D/D=DRYDOWN. This represents the relative rate at which a hybrid will reach acceptable harvest moisture compared to other hybrids on a 1-9 rating scale. A high score indicates a hybrid that dries relatively fast while a low score indicates a hybrid that dries slowly.

D/E=DROPPED EARS. Represented in a 1 to 9 scale in the Characteristics Chart, where 9 is the rating representing the least, or no, dropped ears.

DIP ERS=DIPLODIA EAR MOLD SCORES (Diplodia maydis and Diplodia macrospora). A 1 to 9 visual rating indicating the resistance to Diplodia Ear Mold. A higher score indicates a higher resistance.

DRP EAR=DROPPED EARS. A measure of the number of dropped ears per plot and represents the percentage of plants that did not drop ears prior to harvest.

D/T=DROUGHT TOLERANCE. This represents a 1-9 rating for drought tolerance, and is based on data obtained under stress conditions. A high score indicates good drought tolerance and a low score indicates poor drought tolerance.

EAR HT=EAR HEIGHT. The ear height is a measure from the ground to the highest placed developed ear node attachment and is measured in inches. This is represented in a 1 to 9 scale in the Characteristics Chart, where 9 is highest.

EAR MLD=General Ear Mold. Visual rating (1-9 score) where a "1" is very susceptible and a "9" is very resistant. This is based on overall rating for ear mold of mature ears without determining the specific mold organism, and may not be predictive for a specific ear mold.

EAR SZ=EAR SIZE. A 1 to 9 visual rating of ear size. The higher the rating the larger the ear size.

ECB 1LF=EUROPEAN CORN BORER FIRST GENERATION LEAF FEEDING (Ostrinia nubilalis). A 1 to 9 visual rating indicating the resistance to preflowering leaf feeding by first generation European Corn Borer. A higher score indicates a higher resistance.

ECB 2IT=EUROPEAN CORN BORER SECOND GENERATION INCHES OF TUNNELING (Ostrinia nubilalis). Average inches of tunneling per plant in the stalk.

ECB 2SC=EUROPEAN CORN BORER SECOND GENERATION (Ostrinia nubilalis). A 1 to 9 visual rating indicating post flowering degree of stalk breakage and other evidence of feeding by European Corn Borer, Second Generation. A higher score indicates a higher resistance.

ECB DPE=EUROPEAN CORN BORER DROPPED EARS (Ostrinia nubilalis). Dropped ears due to European Corn Borer. Percentage of plants that did not drop ears under second generation corn borer infestation.

E/G=EARLY GROWTH. This represents a 1 to 9 rating for early growth, scored when two leaf collars are visible.

EST GNT=EARLY STAND COUNT. This is a measure of the stand establishment in the spring and represents the number of plants that emerge on per plot basis for the inbred or hybrid.

EYE SPT=Eye Spot (Kabatiella zeae or Aureobasidium zeae). A 1 to 9 visual rating indicating the resistance to Eye Spot. A higher score indicates a higher resistance.

FUS ERS=FUSARIUM EAR ROT SCORE (Fusarium moniliforme or Fusarium subglutinans). A 1 to 9 visual rating indicating the resistance to Fusarium ear rot. A higher score indicates a higher resistance.

G/A=GRAIN APPEARANCE. Appearance of grain in the grain tank (scored down for mold, cracks, red streak, etc.).

GDU=Growing Degree Units. Using the Barger Heat Unit Theory, that assumes that maize growth occurs in the temperature range 50° F.-86° F. and that temperatures outside this range slow down growth; the maximum daily heat unit accumulation is 36 and the minimum daily heat unit accumulation is 0. The seasonal accumulation of GDU is a major factor in determining maturity zones.

GDU PHY=GDU TO PHYSIOLOGICAL MATURITY. The number of growing degree units required for an inbred or hybrid line to have approximately 50 percent of plants at physiological maturity from time of planting. Growing degree units are calculated by the Barger method.

GDU SHD=GDU TO SHED. The number of growing degree units (GDUs) or heat units required for an inbred line or hybrid to have approximately 50 percent of the plants shedding pollen and is measured from the time of planting. Growing degree units are calculated by the Barger Method, where the heat units for a 24-hour period are: ##EQU1##

The highest maximum temperature used is 86° F. and the lowest minimum temperature used is 50° F. For each inbred or hybrid it takes a certain number of GDUs to reach various stages of plant development.

GDU SLK=GDU TO SILK. The number of growing degree units required for an inbred line or hybrid to have approximately 50 percent of the plants with silk emergence from time of planting. Growing degree units are calculated by the Barger Method as given in GDU SHD definition.

GIB ERS=GIBBERELLA EAR ROT (PINK MOLD) (Gibberella zeae). A 1 to 9 visual rating indicating the resistance to Gibberella Ear Rot. A higher score indicates a higher resistance.

GLF SPT=Gray Leaf Spot (Cercospora zeae-maydis). A 1 to 9 visual rating indicating the resistance to Gray Leaf Spot. A higher score indicates a higher resistance.

GOS WLT=Goss' Wilt (Corynebacterium nebraskense). A 1 to 9 visual rating indicating the resistance to Goss' Wilt. A higher score indicates a higher resistance.

GRN APP=GRAIN APPEARANCE. This is a 1 to 9 rating for the general appearance of the shelled grain as it is harvested based on such factors as the color of harvested grain, any mold on the grain, and any cracked grain. High scores indicate good grain quality.

H/POP=YIELD AT HIGH DENSITY. Yield ability at relatively high plant densities on 1-9 relative rating system with a higher number indicating the hybrid responds well to high plant densities for yield relative to other hybrids. A 1, 5, and 9 would represent very poor, average, and very good yield response, respectively, to increased plant density.

HC BLT=HELMINTHOSPORIUM CARBONUM LEAF BLIGHT (Helminthosporium carbonum). A 1 to 9 visual rating indicating the resistance to Helminthosporium infection. A higher score indicates a higher resistance.

HD SMT=Head Smut (Sphacelotheca reiliana). This score indicates the percentage of plants not infected.

INC D/A=GROSS INCOME (DOLLARS PER ACRE). Relative income per acre assuming drying costs of two cents per point above 15.5 percent harvest moisture and current market price per bushel.

INCOME/ACRE. Income advantage of hybrid to be patented over other hybrid on per acre basis.

INC ADV=GROSS INCOME ADVANTAGE. GROSS INCOME advantage of variety #1 over variety #2.

L/POP=YIELD AT LOW DENSITY. Yield ability at relatively low plant densities on a 1-9 relative system with a higher number indicating the hybrid responds well to low plant densities for yield relative to other hybrids. A 1, 5, and 9 would represent very poor, average, and very good yield response, respectively, to low plant density.

MDM CPX=Maize Dwarf Mosaic Complex (MDMV=Maize Dwarf Mosaic Virus and MCDV=Maize Chlorotic Dwarf Virus). A 1 to 9 visual rating indicating the resistance to Maize Dwarf Mosaic Complex. A higher score indicates a higher resistance.

MOIST=Percent of moisture in chopped whole plant silage.

MST=HARVEST MOISTURE. The moisture is the actual percentage moisture of the grain at harvest.

MST ADV=MOISTURE ADVANTAGE. The moisture advantage of variety #1 over variety #2 as calculated by: MOISTURE of variety #2-MOISTURE of variety #1=MOISTURE ADVANTAGE of variety #1.

NLF BLT=Northern Leaf Blight (Helminthosporium turcicum or Exserohilum turcicum). A 1 to 9 visual rating indicating the resistance to Northern Leaf Blight. A higher score indicates a higher resistance.

OIL=GRAIN OIL. The amount of the kernel that is oil, expressed as a percentage on a dry weight basis.

PHY CRM=CRM at physiological maturity.

PLT HT=PLANT HEIGHT. This is a measure of the height of the plant from the ground to the tip of the tassel in inches. This is represented as a 1 to 9 scale, 9 highest, in the Characteristics Chart.

POL SC=POLLEN SCORE. A 1 to 9 visual rating indicating the amount of pollen shed. The higher the score the more pollen shed.

POL WT=POLLEN WEIGHT. This is calculated by dry weight of tassels collected as shedding commences minus dry weight from similar tassels harvested after shedding is complete.

It should be understood that the inbred can, through routine manipulation of cytoplasmic or other factors, be produced in a male-sterile form. Such embodiments are also contemplated within the scope of the present claims.

POP K/A=PLANT POPULATIONS. Measured as 1000s per acre.

POP ADV=PLANT POPULATION ADVANTAGE. The plant population advantage of variety #1 over variety #2 as calculated by PLANT POPULATION of variety #2-PLANT POPULATION of variety #1=PLANT POPULATION ADVANTAGE of variety #1.

PRM=PREDICTED Relative Maturity. This trait, predicted relative maturity, is based on the harvest moisture of the grain. The relative maturity rating is based on a known set of checks and utilizes standard linear regression analyses and is referred to as the Comparative Relative Maturity Rating System that is similar to the Minnesota Relative Maturity Rating System.

PRM SHD=A relative measure of the growing degree units (GDU) required to reach 50% pollen shed. Relative values are predicted values from the linear regression of observed GDU's on relative maturity of commercial checks.

PRO=PROTEIN RATING . Rating on a 1 to 9 scale comparing relative amount of protein in the grain compared to hybrids of similar maturity. A "1" score difference represents a 0.4 point change in grain protein percent (e.g., 8.0% to 8.4%).

PROTEIN=GRAIN PROTEIN. The amount of the kernel that is crude protein, expressed as a percentage on a dry weight basis.

P/Y=PROTEINNIELD RATING. Indicates, on a 1 to 9 scale, the economic value of a hybrid for swine and poultry feeders. This takes into account the income due to yield, moisture and protein content.

ROOTS (%)=Percent of stalks NOT root lodged at harvest.

R/L=ROOT LODGING. A 1 to 9 rating indicating the level of root lodging resistance. The higher score represents higher levels of resistance.

RT LDG=ROOT LODGING. Root lodging is the percentage of plants that do not root lodge; plants that lean from the vertical axis as an approximately 30° angle or greater would be counted as root lodged.

RTL ADV=ROOT LODGING ADVANTAGE. The root lodging advantage of variety #1 over variety #2.

S/L=STALK LODGING. A 1 to 9 rating indicating the level of stalk lodging resistance. The higher scores represent higher levels of resistance.

SCT GRN=SCATTER GRAIN. A 1 to 9 visual rating indicating the amount of scatter grain (lack of pollination or kernel abortion) on the ear. The higher the score the less scatter grain.

SDG VGR=SEEDLING VIGOR. This is the visual rating (1 to 9) of the amount of vegetative growth after emergence at the seedling stage (approximately five leaves). A higher score indicates better vigor.

SEL IND=SELECTION INDEX. The selection index gives a single measure of the hybrid's worth based on information for up to five traits. A maize breeder may utilize his or her own set of traits for the selection index. One of the traits that is almost always included is yield. The selection index data presented in the tables represent the mean value averaged across testing stations.

SLF BLT=SOUTHERN LEAF BLIGHT (Helminthosporium maydis or Bipolaris maydis). A 1 to 9 visual rating indicating the resistance to Southern Leaf Blight. A higher score indicates a higher resistance.

SLK CRM=CRM at Silking.

SOU RST=SOUTHERN RUST (Puccinia polysora). A 1 to 9 visual rating indicating the resistance to Southern Rust. A higher score indicates a higher resistance.

STA GRN=STAY GREEN. Stay green is the measure of plant health near the time of black layer formation (physiological maturity). A high score indicates better late-season plant health.

STAND (%)=Percent of stalks standing at harvest.

STARCH=GRAIN STARCH. The amount of the kernel that is starch, expressed as a percentage on a dry weight basis.

STD ADV=STALK STANDING ADVANTAGE. The advantage of variety #1 over variety #2 for the trait STK CNT.

STK CNT=NUMBER OF PLANTS. This is the final stand or number of plants per plot.

STK LDG=STALK LODGING. This is the percentage of plants that did not stalk lodge (stalk breakage) as measured by either natural lodging or pushing the stalks and determining the percentage of plants that break below the ear.

STR=PERCENT OF STARCH. This is the percent of dry matter that is starch in chopped whole plant forage.

STW WLT=Stewart's Wilt (Erwinia stewartii). A 1 to 9 visual rating indicating the resistance to Stewart's Wilt. A higher score indicates a higher resistance.

TAS BLS=TASSEL BLAST. A 1 to 9 visual rating was used to measure the degree of blasting (necrosis due to heat stress) of the tassel at the time of flowering. A 1 would indicate a very high level of blasting at time of flowering, while a 9 would have no tassel blasting.

TAS SZ=TASSEL SIZE. A 1 to 9 visual rating was used to indicate the relative size of the tassel. The higher the rating the larger the tassel.

TAS WT=TASSEL WEIGHT. This is the average weight of a tassel (grams) just prior to pollen shed.

TEX EAR=EAR TEXTURE. A 1 to 9 visual rating was used to indicate the relative hardness (smoothness of crown) of mature grain. A 1 would be very soft (extreme dent) while a 9 would be very hard (flinty or very smooth crown).

TIL LER=TILLERS. A count of the number of tillers per plot that could possibly shed pollen was taken. Data are given as a percentage of tillers: number of tillers per plot divided by number of plants per plot.

TST WT (CHARACTERISTICS CHART)=Test weight on a 1 to 9 rating scale with a 9 being the highest rating.

TST WT=TEST WEIGHT (UNADJUSTED). The measure of the weight of the grain in pounds for a given volume (bushel).

TST WTA=TEST WEIGHT ADJUSTED. The measure of the weight of the grain in pounds for a given volume (bushel) adjusted for 15.5 percent moisture.

TSW ADV=TEST WEIGHT ADVANTAGE. The test weight advantage of variety #1 over variety #2.

WIN M%=PERCENT MOISTURE WINS.

WIN Y%=PERCENT YIELD WINS.

YIELD=YIELD OF SILAGE. Yield in tons per acre at 70% moisture.

YLD=YIELD. It is the same as BU ACR ABS.

YLD ADV=YIELD ADVANTAGE. The yield advantage of variety #1 over variety #2 as calculated by: YIELD of variety #1-YIELD variety #2=yield advantage of variety #1.

YLD SC=YIELD SCORE. A 1 to 9 visual rating was used to give a relative rating for yield based on plot ear piles. The higher the rating the greater visual yield appearance.

DETAILED DESCRIPTION OF THE INVENTION

Pioneer Brand Hybrid 31G20 has excellent, stable grain yield. The hybrid shows strong stalks and good resistance to Northern Leaf Blight. 31G20 exhibits excellent stay green above average early growth. It also exhibits excellent husk cover and very good resistance to Gray Leaf Spot, Southern Leaf Blight and Northern Leaf Blight. Hybrid 31G20 exhibits good test weight and is adapted to no-till environments. It is well suited to the Southcentral and Southeast regions of the United States.

Pioneer Brand Hybrid 31G20 is a single cross, yellow endosperm, dent maize hybrid. Hybrid 31G20 has a relative maturity of approximately 119 based on the Comparative Relative Maturity Rating System for harvest moisture of grain.

This hybrid has the following characteristics based on the data collected primarily at Johnston, Iowa.

                                      TABLE 1                                      __________________________________________________________________________     VARIETY DESCRIPTION INFORMATION                                                VARIETY = 31G20                                                                __________________________________________________________________________       TYPE: (describe intermediate types in Comments section):                        2   1 = Sweet 2 = Dent 3 = Flint 4 = Flour 5 = Pop 6 = Ornamental             MATURITY:                                                                         DAYS HEAT UNITS                                                           076   1,412.0 From emergence to 50% of plants in silk                          077          1,440.0 From emergence to 50% of plants in pollen                 003          0,078.0 From l0% to 90% pollen shed                               065          1,289.0 From 50% silk to harvest at 25% moisture                                                       Standard                                                                            Sample                                 PLANT:                                                                                                                 Size                Deviation          0,300.0                                                                             cm                                                                               Plant Height (to tassel tip)                                                                                      2        7.07                        0,137.5                                                                             cm                                                                               Ear Height (to base of top ear node)                                                                              2   3.54                             0,018.9                                                                             cm                                                                               Length of Top Ear Internode          10   0.71                          0.1    Average Number of Tillers          2        0.17                        1.0    Average Number of Ears per Stalk                                                                                  2    0.00                          2.0      Anthocyanin of Brace Roots: 1 = Absent 2 = Faint 3 = Moderate 4                = Dark                                                                  LEAF:                              Standard                                                                            Sample                                                                         Size             Deviation                 011.1                                                                             cm                                                                             Width of Ear Node Leaf               10        0.71                         099.5                                                                             cm                                                                             Length of Ear Node Leaf              10       2.69                          08.0                                                                                 Number of leaves above top ear                                                                                   10   1.41                           049.0                                                                                 Degrees Leaf Angle (measure from 2nd leaf above                                                                  290                                                     ear at anthesis to stalk above leaf)                      03       Leaf Color                                                                            Dark Green                                                                             (Munsell code)   5GY34                                 1.0      Leaf Sheath Pubescence (Rate on scale from 1 = none to 9 = like                peach fuzz)                                                           4.0           Marginal Waves (Rate on scale from 1 = none to 9 = many)         6.5           Longitudinal Creases (Rate on scale from 1 = none to 9 =                  many)                                                                   TASSEL:                            Standard                                                                            Sample                                                                    Deviation                                                                           Size                                   07.4      Number of Primary Lateral Branches                                                                             10    0.28                           038.0                                                                                     Branch Angle from Central Spike                                                                                2    7.07                            61.4                                                                                 cm                                                                              Tassel Length (from top leaf collar to tassel                                                                5.66                                                                                2                                   8.0    Pollen Shed (rate on scale from 0 = male sterile to 9 = heavy                  shed)                                                                 17       Anther Color                                                                          Purple  (Munsell code)   5RP510                                01             Glume Color                                                                         Light Green                                                                           (Munsell code)                                                                                     5GY68                           1.0      Bar Glumes (Glume Bands): 1 = Absent 2 = present                      25             Peduncle Length (cm. from top leaf to basal branches)           6a.                                                                              EAR (Unhusked Data):                                                         1    Silk Color (3 days after emergence) Light Green                                                          (Munsell code)                                                                              2.5GY96                            2     Fresh Husk Color (25 days after 50% silking) Medium                                                       (Munsell code)                                                                                  5GY56                        21   Dry Husk Color (65 days after 50% silking)                                                          Buff (Munsell code)                                                                              2.5Y8.54                           1    Position of Ear at Dry Husk Stage: 1 = Upright 2 = Horizontal 3 =              Pendant                                   Upright                         7     Husk Tightness (Rate of Scale from 1 = very loose to 9 = very                 tight)                                                                    2     Husk Extension (at harvest): 1 = Short (ears exposed) 2 = Medium (<           8 cm)                                                                                3 = Long (8-10 cm beyond ear tip) 4 = Very Long (> l0                                                                      Medium                                                       Standard                                                                            Sample                               6b.                                                                                  EAR (Husked Ear Data):                                                                                        Deviation                                                                             Size                               21     cm Ear Length                 0.00 10                                   46     mm Ear Diameter at mid-point          10        0.00                    230    gm Ear Weight                         10               18.38            17         Number of Kernel Rows             10           0.71                 2          Kernel Rows: 1 = Indistinct 2 = Distinct                                                                           Distinct                        1         Row Alignment: 1 = Straight 2 = Slightly Curved 3                                                            piral        Straight                  14     cm Shank Length                       10               2.12             2         Ear Taper: 1 = Slight 2 = Average 3 = Extreme                                                                       Average                           KERNEL (Dried):                    Standard                                                                            Sample                                                                    Deviation                                                                            Size                                12     mm Kernel Length              0.00 10                                   8      mm Kernel Width                       10                  0.00          5      mm Kernel Thickness                   10              0.71              23         % Round Kernels (Shape Grade)                                                                                     2       4.95                     1        Aleurone Color Pattern: 1 = Homozygous 2 = Segregating                                                               Homozygous                      7        Aluerone Color Yellow       (Munsell code)                                                                           10YR714                         7          Hard Endosperm Color                                                                               Yellow                                                                                       (Munsell code)                                                                           1.25Y814                3          Endosperm Type:                                                                                      Normal Starch                                          1 = Sweet (Sul) 2 = Extra Sweet (sh2) 3 = Normal Starch                        4 = High Amylose Starch 5 = Waxy Starch 6 = High Protein                       7 = High Lysine 8 = Super Sweet (se) 9 = High Oil                              10 = Other ------                                                     35     gm Weight per 100 Kernels (unsized sample)                                                                   2.12 2                                                                         Sample                                      COB: Standard                                                                                                     Deviation                                                                            Size                                25     mm Cob Diameter at mid-point  0.71 10                                   14        Cob Color  Red             (Munsell code)                                                                           10R38                             DISEASE RESISTANCE (Rate from 1 (most susceptible) to 9 (most                  resistant); leave blank                                                        if not tested; leave Race or Strain Options blank if polygenic):             A. Leaf Blights, Wilts, and Local Infection Diseases                                     Anthracnose Leaf Blight (Colletotrichum graminicola)                         5   Common Rust (Puccinia sorghi)                                                  Common Smut (Ustilago maydis)                                                  Eyespot (Kabatiella zeae)                                                      Goss's Wilt (Clavibacter michiganense spp. nebraskense)                    6   Gray Leaf Spot (Cercospora zeae-maydis)                                        Helminthosporium Leaf Spot (Bipolaris zeicola) Race ------                 7   Northern Leaf Blight (Exserohilum turcicum)   Race ------                  6   Southern Leaf Blight (Bipolaris maydis)   Race ------                      5   Southern Rust (Puccinia polysora)                                          8   Stewart's Wilt (Erwinia stewartii)                                             Other (Specify) ------                                             B. Systemic Diseases                                                                   5 Corn Lethal Necrosis (MCMV and MDMV)                                             Head Smut (Sphacelotheca reiliana)                                             Maize Chlorotic Dwarf Virus (MDV)                                              Maize Chlorotic Mottle Virus (MCMV)                                        3   Maize Dwarf Mosaic Virus (MDMV)                                                Sorghum Downy Mildew of Corn (Peronosclerospora sorghi)                        Other (Specify) ------                                             C. Stalk Rots                                                                          5 Anthracnose Stalk Rot (Colletotrichum graminicola)                               Diplodia Stalk Rot (Stenocarpella maydis)                                      Fusarium Stalk Rot (Fusarium moniliforme)                                      Gibberella Stalk Rot (Gibberella zeae)                                         Other (Specify) ------                                             D. Ear and Kernel Rots                                                                   Aspergillus Ear and Kernel Rot (Aspergillus flavus)                          5   Diplodia Ear Rot (Stenocarpella maydis)                                    6   Fusarium Ear and Kernel Rot (Fusarium moniliforme)                             Gibberella Ear Rot (Gibbereila zeae)                                           Other (Specify) ------                                                          Banks grass Mite (Oligonychus pratensis)                                      Corn Worm (Helicoverpa zea)                                                     Leaf Feeding                                                                   SiIk Feeding                                                                  mg Iarval wt.                                                                  Ear Damage                                                                     Corn Leaf Aphid (Rhopalosiphum maidis)                                         Corn Sap Beetle (Carpophilus dimidiatus                                        European Corn Borer (Ostrinia nubilalis)                                   4    1st Generation typicalIy Whorl Leaf Feeding)                              7    2nd Generation (TypicaIly Leaf Sheath-ColIar Feeding)                          Stalk Tunneling                                                           cm                                                                               tunneled/plant                                                                   Fall Armyworm (Spodoptera fruqiperda)                                           Leaf Feeding                                                                   Silk Feeding                                                                   mg Iarval wt.                                                                 Maize Weevil (Sitophilus zeamaize                                              Northern Rootworm (Diabrotica barberi)                                         Southern Rootworm (Diabrotica undecimpunctata)                                 Southwestern Corn Borer (Diatreaea grandiosella)                                Leaf Feeding                                                                   Stalk Tunneling                                                               cm tunneled/plant                                                               Two-spotted Spider Mite (Tetranychus urticae)                                  Western Rootworm (Diabrotica virgifrea virgifera)                              Other (Specify) ------                                                    11.                                                                              AGRONOMIC TRAITS:                                                            5   Staygreen (at 65 days after anthesis) (Rate on a scale from 1                = worst to 9 = excellent)                                                    1.9                                                                                % Dropped Ears (at 65 days after anthesis)                                     % Pre-anthesis Brittle Snapping                                                % Pre-anthesis Root Lodging                                        10.2       Post-anthesis Root Lodging (at 65 days after anthesis)              10,287           Kg/ha Yield (at 12-13% grain moisture)                        __________________________________________________________________________      *In interpreting the foregoing color designations, reference may be had t      the Munsell Glossy Book of Color, a standard color reference.            

Research Comparisons for Pioneer Hybrid 31G20

Comparisons of characteristics for Pioneer Brand Hybrid 31G20 were made against Pioneer Brand Hybrids 32K61, 3223, and 3163.

Table 2A compares Pioneer Brand Hybrid 31G20 and Pioneer Brand Hybrid 32K61, a genetically related hybrid. The results show that the 31G20 hybrid demonstrates a significantly larger early stand count than the 32K61 hybrid. Hybrid 31G20 demonstrates a significantly larger stalk count and significantly superior resistance to Northern Leaf Blight than hybrid 32K61. Hybrid 31G20 also exhibits significantly higher ear placement than hybrid 32K61.

Table 2B compares Pioneer Brand Hybrid 31G20 and Pioneer Brand Hybrid 3223, a hybrid with a similar area of adaptation. The results show that the 31G20 hybrid demonstrates significantly superior test weight than the 3223 hybrid. Hybrid 31G20 demonstrates significantly superior seedling vigor and a significantly better stay green score than hybrid 3223. Hybrid 31G20 also demonstrates significantly better resistance to stalk lodging and a significantly larger stalk count than hybrid 3223 as well as significantly superior resistance to Southern Leaf Blight and to Gray Leaf Spot compared to hybrid 3223.

Table 2C compares Pioneer Brand Hybrid 31G20 and Pioneer Brand Hybrid 3163, a hybrid with similar maturity and adaptation. According to the results the 31G20 hybrid is significantly higher yielding than the 3163 hybrid. Hybrid 31G20 demonstrates a significantly higher test weight and significantly superior seedling vigor than hybrid 3163. Hybrid 31G20 also exhibits significantly superior resistance to stalk lodging and to root lodging than hybrid 3163. 31G20 further displays a significantly larger stalk count as well as a significantly larger early stand count compared to hybrid 3163. Finally, hybrid 31G20 exhibits significantly better resistance to Gray Leaf Spot than the 3163 hybrid.

                                      TABLE 2A                                     __________________________________________________________________________     HYBRID COMPARISON REPORT                                                       VARIETY #1 = 31G20                                                             VARIETY #2 = 32K61                                                             __________________________________________________________________________                    PRM BU  BU      TST SDG EST GDU                                            PRM     SHD                                                                              ACR                                                                                  ACR                                                                               MST                                                                                 WT                                                                                VGR                                                                                 CNT                                                                               SHD                                         ABS     ABS                                                                              ABS                                                                                  % MN                                                                              % MN                                                                               ABS                                                                                % MN                                                                                % MN                                                                              % MN                             __________________________________________________________________________     TOTAL SUM                                                                               1     120                                                                                116                                                                            168.1                                                                                  105                                                                               104                                                                               57.2                                                                                102                                                                                 105                                                                               102                                       2     116                                                                                116                                                                            167.2                                                                                  104                                                                                95                                                                               58.3                                                                                104                                                                                 100                                                                               101                                       LOCS                                                                               11                                                                                  4                                                                                 136                                                                                  136                                                                               138                                                                                 54                                                                                 43                                                                               42                                                                                   22                                       REPS                                                                               11                                                                                  4                                                                                 153                                                                                  153                                                                               155                                                                                 54                                                                                 46                                                                               44                                                                                   23                                       DIFF                                                                                4                                                                                  1                                                                                 0.9                                                                                 1                                                                                 9    1.0                                                                               2    5                                                                                 1                                        PR > T                                                                              .000#                                                                             .495                                                                               .662                                                                               .424                                                                               .000#                                                                              .003#                                                                              .630                                                                               .006#                                                                              .300                                __________________________________________________________________________                GDU     STK                                                                              PLT                                                                                  EAR                                                                                RT                                                                                STA                                                                                STK                                                                                 BRT                                                                               DRP                                         SLK     CNT                                                                               HT                                                                                HT                                                                                  LDG                                                                                GRN                                                                                LDG                                                                                 STK                                                                               EAR                                         % MN                                                                                   % MN                                                                             % MN                                                                                 % MN                                                                              % MN                                                                               % MN                                                                               % MN                                                                                % MN                                                                              % MN                             __________________________________________________________________________     TOTAL SUM                                                                               1     101                                                                                103                                                                              103                                                                                  101                                                                               106                                                                                108                                                                                106                                                                                 100                                                                                97                                       2     101                                                                                101                                                                              102                                                                                97                                                                                  104                                                                                111                                                                                110                                                                                 100                                                                               101                                       LOCS                                                                               13                                                                                   156                                                                               49                                                                                49                                                                                   40                                                                                 63                                                                                 72                                                                                2                                                                                   11                                       REPS                                                                               14                                                                                   196                                                                               64                                                                                64                                                                                   42                                                                                 74                                                                                 76                                                                                2                                                                                   12                                       DIFF                                                                                0                                                                                  2                                                                                 0   5   3   3   4    0                                                                                 3                                        PR > T                                                                             .999                                                                               .000#                                                                              .999                                                                               .001#                                                                              .438                                                                               .484                                                                               .029+                                                                              .999                                                                               .043+                               __________________________________________________________________________                GLF     NLF                                                                              SLF                                                                                  STW                                                                               ANT                                                                                 HD                                                                                MDM                                                                                 FUS                                                                               DIP                                         SPT     BLT                                                                              BLT                                                                                  WLT                                                                               ROT                                                                                SMT                                                                                CPX                                                                                 ERS                                                                               ERS                                         ABS     ABS                                                                              ABS                                                                                  ABS                                                                               ABS                                                                                ABS                                                                                ABS                                                                                 ABS                                                                               ABS                              __________________________________________________________________________     TOTAL SUM                                                                               1     5.9                                                                                7.0                                                                              6.5                                                                                  8.0                                                                               4.8                                                                              100.0                                                                                3.5                                                                                 7.5                                                                               5.0                                       2     5.7                                                                                6.0                                                                              6.3                                                                                  8.0                                                                               5.0                                                                              100.0                                                                                2.8                                                                                 7.0                                                                               4.5                                       LOCS                                                                                5                                                                                  2                                                                                   3                                                                                 1                                                                                 2   1   3    2                                                                                 1                                          REPS                                                                                6                                                                                  4                                                                                   4                                                                                 1                                                                                 4   2   6    2                                                                                 2                                          DIFF                                                                                 0.2                                                                                1.0                                                                              0.2                                                                                  0.0                                                                               0.3                                                                                0.0                                                                                0.7                                                                                 0.5                                                                               0.5                                     PR > T                                                                             .621                                                                               .000#                                                                              .885                                                                                     .500                                                                                   .270                                                                                .500                                 __________________________________________________________________________                COM  SOU                                                                                 ECB                                                                  RST  RST                                                                                 2SC                                                                  ABS  ABS                                                                                 ABS                                                       __________________________________________________________________________     TOTAL SUM                                                                               1    4.6                                                                              4.5                                                                                 6.0                                                                2    5.8                                                                              4.0                                                                                 6.0                                                                LOCS                                                                               8    4                                                                                   1                                                                REPS                                                                               8    4                                                                                   1                                                                DIFF                                                                                1.1                                                                              0.5                                                                                 0.0                                                               PR > T                                                                            .002#                                                                              .391                                                            __________________________________________________________________________      * = 10% SIG                                                                    + = 5% SIG                                                                     # = 1% SIG                                                               

                                      TABLE 2B                                     __________________________________________________________________________     HYBRID COMPARISON REPORT                                                       VARIETY #1 = 31G20                                                             VARIETY #2 = 3223                                                              __________________________________________________________________________                    PRM BU  BU      TST  SDG                                                                               EST GDU                                            PRM   SHD                                                                                ACR                                                                                 ACR                                                                               MST                                                                                WT                                                                                  VGR                                                                               CNT                                                                                SHD                                          ABS   ABS                                                                                ABS                                                                                 % MN                                                                              % MN                                                                                 ABS                                                                               % MN                                                                              % MN                                                                               % MN                              __________________________________________________________________________     TOTAL SUM                                                                                1                                                                                   119                                                                              117                                                                              174.3                                                                                 105                                                                               105                                                                                 57.3                                                                               107                                                                               103                                                                                102                                         2                                                                                   116                                                                              118                                                                              171.3                                                                                 103                                                                                96                                                                                 56.0                                                                                87                                                                               102                                                                                102                                         LOCS                                                                              17                                                                                   9                                                                                166                                                                                 166                                                                               170                                                                                61                                                                                   66                                                                                58                                                                                 26                                         REPS                                                                              17                                                                                   9                                                                                199                                                                                 199                                                                               203                                                                                63                                                                                   72                                                                                60                                                                                 29                                         DIFF                                                                               4                                                                                   1                                                                                3.0                                                                                2     9                                                                                  1.3                                                                                20                                                                                 1                                                                                  0                                      PR > T                                                                             .000#                                                                              .323                                                                               .142                                                                               .127                                                                               .000#                                                                              .000#                                                                              .000#                                                                              .276                                                                               .999                                __________________________________________________________________________                GDU   STK                                                                                PLT                                                                                 EAR                                                                                 RT                                                                                STA                                                                                STK                                                                               BRT                                                                                GRN                                          SLK   CNT                                                                                 HT                                                                                  HT                                                                                LDG                                                                                GRN                                                                                LDG                                                                               STK                                                                                APP                                          % MN                                                                                 % MN                                                                               % MN                                                                                % MN                                                                               % MN                                                                               % MN                                                                               % MN                                                                              % MN                                                                               % MN                              __________________________________________________________________________     TOTAL SUM                                                                                1                                                                                   102                                                                              103                                                                                103                                                                                 102                                                                                100                                                                                113                                                                                106                                                                                98                                                                                109                                         2                                                                                   102                                                                              100                                                                                100                                                                                 106                                                                                100                                                                                 95                                                                                 97                                                                               101                                                                                101                                         LOCS                                                                              17                                                                                 191                                                                                 69                                                                                  69                                                                                 43                                                                                 79                                                                                 95                                                                                 4                                                                                  3                                         REPS                                                                              20                                                                                 245                                                                                 87                                                                                  87                                                                                 51                                                                                 95                                                                                107                                                                                 5                                                                                  3                                         DIFF                                                                               0                                                                                   3                                                                                  2                                                                                5   0     18                                                                                 10                                                                                 3                                                                                  8                                      PR > T                                                                             .999                                                                               .004#                                                                              .001#                                                                              .000#                                                                              .999                                                                               .000#                                                                              .005#                                                                              .351                                                                               .184                                __________________________________________________________________________                DRP   GLF                                                                                NLF                                                                                 SLF                                                                               STW                                                                                  ANT                                                                                HD                                                                                   MDM                                          EAR   SPT                                                                                BLT                                                                                 BLT                                                                               WLT                                                                                  ROT                                                                               SMT                                                                               CLN                                                                                CPX                                          % MN                                                                                 ABS                                                                                ABS                                                                                 ABS                                                                               ABS                                                                                  ABS                                                                               ABS                                                                               ABS                                                                                ABS                               __________________________________________________________________________     TOTAL SUM                                                                                1                                                                                   100                                                                              6.3                                                                                6.5                                                                                 6.3                                                                               8.0                                                                                  4.8                                                                             100.0                                                                               5.0                                                                                3.3                                         2                                                                                   101                                                                              2.6                                                                                6.7                                                                                 3.2                                                                               8.0                                                                                  4.4                                                                             100.0                                                                               7.5                                                                                4.1                                         LOCS                                                                              20                                                                                  12                                                                                  6                                                                                5     1                                                                                 4                                                                                 1     1                                                                                  4                                         REPS                                                                              22                                                                                  17                                                                                 12                                                                                7     1                                                                                 7                                                                                 2     2                                                                                  8                                         DIFF                                                                               1                                                                                 3.7                                                                                0.2                                                                                 3.1                                                                               0.0                                                                                  0.4                                                                               0.0                                                                               2.5                                                                                0.9                                       PR > T                                                                            .418                                                                               .000#                                                                              .732                                                                               .001#   .058*                                                                                       .235                               __________________________________________________________________________                FUS   DIP                                                                                COM                                                                                SOU                                                                                  ECB                                                                             ECB                                                       ERS   ERS                                                                                RST                                                                                RST                                                                                  1LF                                                                             2SC                                                       ABS   ABS                                                                                ABS                                                                                ABS                                                                                  ABS                                                                             ABS                                            __________________________________________________________________________     TOTAL SUM                                                                                1                                                                                   6.0                                                                              5.0                                                                                4.6                                                                                4.5                                                                                  4.0                                                                             7.1                                                      2                                                                                   5.8                                                                              3.8                                                                                2.6                                                                                3.8                                                                                  2.8                                                                             4.4                                                      LOCS                                                                               3                                                                                   2                                                                                  8                                                                                  4                                                                                 4                                                                                  8                                                      REPS                                                                               4                                                                                   4                                                                                  8                                                                                  4                                                                                 4                                                                                 11                                                      DIFF                                                                                0.2                                                                              1.3                                                                                2.1                                                                                0.8                                                                                  1.3                                                                             2.7                                                   PR > T                                                                             .914                                                                               .344                                                                               .000#                                                                              .444                                                                               .015+                                                                              .001#                                           __________________________________________________________________________      * = 10% SIG                                                                    + = 5% SIG                                                                     # = 1% SIG                                                               

                                      TABLE 2C                                     __________________________________________________________________________     HYBRID COMPARISON REPORT                                                       VARIETY #1 = 31G20                                                             VARIETY #2 = 3163                                                              __________________________________________________________________________                    PRM BU  BU      TST SDG EST GDU                                            PRM  SHD                                                                                  ACR                                                                               ACR                                                                                  MST                                                                                WT                                                                                VGR                                                                                CNT                                                                               SHD                                          ABS  ABS                                                                                  ABS                                                                               % MN                                                                                 % MN                                                                              ABS                                                                                % MN                                                                               % MN                                                                              % MN                              __________________________________________________________________________     TOTAL SUM                                                                                1                                                                                   119                                                                             117                                                                                167.5                                                                               106                                                                                  102                                                                              57.5                                                                                106                                                                                104                                                                               102                                         2                                                                                   119                                                                             116                                                                                164.3                                                                               104                                                                                  101                                                                              55.9                                                                                 95                                                                                 99                                                                               102                                         LOCS                                                                              16                                                                                  9                                                                                  233                                                                               233                                                                                  239                                                                                99                                                                                 60                                                                                 55                                                                                25                                         REPS                                                                              16                                                                                  9                                                                                  265                                                                               265                                                                                  271                                                                               101                                                                                 66                                                                                 57                                                                                28                                         DIFF                                                                               0                                                                                  0                                                                                  3.1                                                                                 2                                                                                 2                                                                                  1.6                                                                                 11                                                                               5     0                                      PR > T                                                                             .999                                                                               .999                                                                               .040+                                                                              .062*                                                                              .002#                                                                              .000#                                                                              .003#                                                                              .000#                                                                              .999                                __________________________________________________________________________                GDU  STK                                                                                  PLT                                                                               EAR                                                                                RT                                                                                  STA                                                                                STK                                                                                BRT                                                                               GRN                                          SLK  CNT                                                                                   HT                                                                                HT                                                                                  LDG                                                                               GRN                                                                                LDG                                                                                STK                                                                               APP                                          % MN                                                                                % MN                                                                                 % MN                                                                              % MN                                                                                 % MN                                                                              % MN                                                                               % MN                                                                               % MN                                                                              % MN                              __________________________________________________________________________     TOTAL SUM                                                                                1                                                                                   102                                                                             102                                                                                  103                                                                               101                                                                                  102                                                                               109                                                                                107                                                                                 98                                                                               109                                         2                                                                                   102                                                                              98                                                                                  100                                                                               102                                                                                94                                                                                  109                                                                                 97                                                                                 97                                                                                93                                         LOCS                                                                              16                                                                                229                                                                                   55                                                                                55                                                                                70                                                                                  102                                                                                100                                                                               4     3                                         REPS                                                                              19                                                                                276                                                                                   68                                                                                68                                                                                78                                                                                  116                                                                                112                                                                               5     3                                         DIFF                                                                               0                                                                                  4                                                                                 2     1                                                                                 8                                                                                 1     10                                                                               1    16                                      PR > T                                                                             .999                                                                               .000#                                                                              .004#                                                                              .580                                                                               .003#                                                                              .864                                                                               .001#                                                                              .825                                                                               .057*                               __________________________________________________________________________                DRP  GLF                                                                                  NLF                                                                               SLF                                                                                  STW                                                                               ANT                                                                                 HD                                                                                   MDM                                          EAR  SPT                                                                                  BLT                                                                               BLT                                                                                  WLT                                                                               ROT                                                                                SMT                                                                                CLN                                                                               CPX                                          % MN                                                                                ABS                                                                                  ABS                                                                               ABS                                                                                  ABS                                                                               ABS                                                                                ABS                                                                                ABS                                                                               ABS                               __________________________________________________________________________     TOTAL SUM                                                                                1                                                                                   100                                                                             6.3                                                                                  6.5                                                                               6.3                                                                                  8.0                                                                               4.5                                                                              100.0                                                                                5.0                                                                               3.3                                         2                                                                                   100                                                                             4.0                                                                                  6.1                                                                               6.7                                                                                  5.0                                                                               3.6                                                                               93.8                                                                                5.0                                                                               4.0                                         LOCS                                                                              20                                                                                 12                                                                                 6     5                                                                                 1                                                                                 4   1   1     4                                         REPS                                                                              22                                                                                 17                                                                                   12                                                                                 7                                                                                 1                                                                                 8   2   2     8                                         DIFF                                                                               1                                                                                2.3                                                                                  0.4                                                                               0.4                                                                                  3.0                                                                               0.9                                                                                6.3                                                                                0.0                                                                               0.8                                      PR > T                                                                             .776                                                                               .000#                                                                              .558                                                                               .477                                                                                   .035+                                                                                       .103                               __________________________________________________________________________                FUS  DIP                                                                                COM                                                                                 SOU                                                                               ECB                                                           ERS  ERS                                                                                RST                                                                                 RST                                                                               2SC                                                           ABS  ABS                                                                                ABS                                                                                 ABS                                                                               ABS                                                __________________________________________________________________________     TOTAL SUM                                                                               1     6.0                                                                             5.0                                                                                4.6                                                                                 4.7                                                                               6.6                                                         2     5.7                                                                             4.0                                                                                5.6                                                                                 4.7                                                                               5.0                                                         LOCS                                                                                3                                                                                  2                                                                                  8                                                                                   3                                                                                 4                                                         REPS                                                                                4                                                                                  4                                                                                  8                                                                                   3                                                                                 7                                                         DIFF                                                                                 0.3                                                                             1.0                                                                                1.0                                                                                 0.0                                                                               1.6                                                       PR > T                                                                             .868                                                                               .000#                                                                              .068*                                                                              .999                                                                               .051*                                               __________________________________________________________________________      * = 10% SIG                                                                    + = 5% SIG                                                                     # = 1% SIG                                                               

Strip Test Data for Hybrid 31G20

Comparison data was collected from strip tests that were grown by farmers. Each hybrid was grown in strips of 4, 6, 8, 12, etc. rows in fields depending on the size of the planter used. The data was collected from strip tests that had the hybrids in the same area and weighed. The moisture percentage was determined and bushels per acre was adjusted to 15.5 percent moisture. The number of comparisons represent the number of locations or replications for the two hybrids that were grown in the same field in close proximity and compared.

Comparison strip testing was done between Pioneer Brand Hybrid 31G20 and Pioneer Brand Hybrids 3163, 3223, and 32K61. The comparisons come from all the hybrid's adapted growing areas in the United States.

These results are presented in Table 3. As can be seen from the table hybrid 31G20 has a significant stand and root lodge advantage over the hybrids combined. The average stand and root lodge advantage was one percent more plants that do not have root lodge or that are standing at harvest compared to the other hybrids. Hybrid 31G20's stalk and root lodging advantage plus its advantage for other characteristics over these hybrids will make it an important addition for most of the areas where these hybrids are grown.

                                      TABLE 3                                      __________________________________________________________________________     1997 PERFORAANCE COMPARISON REPORT FOR CORN                                    1 YEAR SUMMARY OF ALL STANDARD TEST TYPES                                      Brand      Product                                                                            Yield                                                                             Moist                                                                             Income/Acre                                                                          Pop K/Acre                                                                           Stand (%)                                                                           Roots (%)                                                                           Test Wt                             __________________________________________________________________________     Pioneer    31G20                                                                              138.8                                                                             19.3                                                                              333.60                                                                               23.6  94   99   58.0                                Pioneer        3163                                                                             141.3                                                                            18.7                                                                              340.87                                                                                23.3                                                                                91    98  56.7                               Advantage      -2.5                                                                              -.6                                                                               -7.27   .3    3    1    1.3                               Number of Comparisons                                                                         112                                                                                 112                                                                               112  88    30    12   108                               Percent Wins                                                                                  35  30                                                                                 35   42    33    17  78                                 Probability of Difference                                                                     91  99                                                                                 96   81    84    71  99                                 Pioneer       31G20                                                                            138.8                                                                             18.3                                                                              335.57                                                                                23.8                                                                                97    98  58.2                               Pioneer        3223                                                                             142.4                                                                            17.0                                                                              347.76                                                                                23.8                                                                                96    97  58.0                               Advantage      -3.6                                                                              -1.3                                                                              -12.19                                                                                 .0    1    1   .2                                 Number of Comparisons                                                                          105                                                                                105                                                                               105  75    20    8    100                               Percent Wins                                                                                   32                                                                                15                                                                                 30   37    35    25  49                                 Probability of Difference                                                                      98                                                                                99                                                                                 99   34    83    52  88                                 Pioneer       31G20                                                                            140.6                                                                             20.2                                                                              335.13                                                                                24.0                                                                                92    99  57.9                               Pioneer        32K61                                                                           142.5                                                                             18.0                                                                              346.25                                                                                23.8                                                                                94   100  59.4                               Advantage        -1.9                                                                            -2.2                                                                              -11.12                                                                                 .2  -2    -1  -1.5                                Number of Comparisons                                                                         152                                                                                 152                                                                               152   117  32    14   139                               Percent Wins                                                                                    38                                                                               13                                                                                 30   44    22    0    9                                 Probability of Difference                                                                      93                                                                                99                                                                                 99   75    58    83  98                                 Pioneer        31G20                                                                           139.5                                                                             19.3                                                                              334.79                                                                                23.8                                                                                94    99  58.0                               Weighted Avg      142.1                                                                           17.9                                                                              345.05                                                                                23.7                                                                                93    98  58.1                               Advantage        -2.6                                                                            -1.4                                                                              -10.26                                                                                 .1    1    1  -.1                                 Number of Comparisons                                                                          369                                                                                369                                                                               369   280  82    34   347                               Percent Wins                                                                                   35                                                                                19                                                                                 31   42    29    12  42                                 Probability of Difference                                                                      99                                                                                99                                                                                 99   85    61    73  27                                 __________________________________________________________________________      NOTE:                                                                          The probability values are useful in analyzing if there is a "real"            difference in the genetic potential of the products involved. High values      are desirable, with 95% considered significant for real differences.     

Characteristics of Pioneer Hybrid 31G20 are compared to Pioneer Hybrids 32K61, 3163, and 3223 in Table 4. The values given for most traits are on a 1-9 basis. In these cases 9 would be outstanding, while 1 would be poor for the given characteristics. Table 4 shows that hybrid 31G20 yields well for its maturity. Hybrid 31G20 also displayed good stalk lodging resistance. The hybrid exhibited a superior husk cover and a better Gray Leaf Spot resistance score than each of the comparison hybrids. Hybrid 31G20's excellent yield combined with its other favorable agronomic characteristics should make it an important hybrid to its area of adaptation.

Comparison of Key Characteristics for Hybrid 31G20

                                      TABLE 4                                      __________________________________________________________________________     Hybrid Patent Comparisons-Characteristics                                      Pioneer Hybrid 31G20 vs. Pioneer Hybrids 32K61, 3163, 3223                     __________________________________________________________________________              SILK                                                                              PHY                                                                               GDU                                                                               GDU                                                          VARIETY                                                                               CRM                                                                                CRM                                                                              CRM                                                                              SILK                                                                               PHY                                                                               YLD                                                                              H/POP                                                                              L/POP                                                                               D/D                                                                               S/L                                                                               R/L                                     __________________________________________________________________________     31G20   119                                                                              116                                                                                117                                                                             1450                                                                              2840                                                                               8          5  8  6                                       32K61   114                                                                              116                                                                                114                                                                             1450                                                                              2760                                                                               9   9   9  5  8  8                                       3163   119                                                                               116                                                                                117                                                                             1450                                                                              2840                                                                               9   7   9  7  4  6                                       3223   116                                                                               117                                                                                115                                                                             1460                                                                              2790                                                                               9   9   8  6  5  6                                       __________________________________________________________________________            STA                                                                                  TST                                                                                  PLT                                                                               EAR                                                                                    BRT                                                                               HSK                                                                               GLF                                                                               NLF                                     VARIETY                                                                               GRN                                                                                D/T                                                                               WT                                                                                E/G                                                                               HT                                                                                HT                                                                                D/E                                                                                STK                                                                                CV                                                                               SPT                                                                               BLT                                     __________________________________________________________________________     31G20   7                                                                                7   7                                                                                6  8  7   4   5  8  7  6                                       32K61   8                                                                                7   8                                                                                5  7  6   5   4  5  6  5                                       3163     8                                                                               7   4                                                                                6  5  6   5   3  4  4  6                                       3223     7                                                                               8   5                                                                                5  8  9   5   3  5  2  6                                       __________________________________________________________________________             GOS                                                                               ANT                                                                               HD                                                                               GIB                                                                               EYE                                                                                ECB                                                                               ECB                                                  VARIETY                                                                                WLT                                                                               ROT                                                                              SMT                                                                               ERS                                                                               SPT                                                                                1LF                                                                               2SC                                                  __________________________________________________________________________     31G20     5           4   5                                                    32K61   8                                                                                5   7                                                                                      4   5                                                    3163     9                                                                               4   6                                                                                7  6  5   5                                                    3223     8                                                                               4   9                                                                                7  3  3   5                                                    __________________________________________________________________________

Silage Data Comparison for Pioneer Hybrid 31G20

Comparison of silage characteristics of Pioneer Brand Hybrid 31G20 were made against Pioneer Brand Hybrids 3172, 3223 and 32K61, all of which are similar in adaptation to 31G20

Table 5A compares Pioneer Hybrid 31G20 to Pioneer Hybrid 3172. The results show that 31G20 produces significantly less moisture in chopped whole plant silage than hybrid 3172. Hybrid 31G20 also exhibits a significantly higher percentage of starch content in dry matter from chopped plant forage.

Table 5B compares Pioneer Hybrid 31G20 to Pioneer Hybrid 3223. The results show that Hybrid 31G20 produces a significantly higher fiber content in its dry matter than hybrid 3223. Hybrid 31G20 produces somewhat lower moisture in chopped whole plant silage and a lower crude protein content in shopped whole plant forage.

Table 5C compares Pioneer Hybrid 31G20 to Pioneer Hybrid 32K61. The results indicate that Hybrid 31G20 produces significantly lower silage moisture content than hybrid 32K61. Hybrid 31G20 also exhibits a significantly higher acid detergent fiber content in whole plant forage.

                  TABLE 5A                                                         ______________________________________                                         HYBRID SILAGE COMPARISON REPORT                                                VARIETY #1 - 31G20                                                             VARIETY #2 - 3172                                                                           YLD/    MOIST   STR   ADF   CP                                           VAR     TA     %       %     %      %                                          #       ABS    ABS      ABS   ABS  ABS                                  ______________________________________                                         TOTAL SUM                                                                               1       33.0    65.23 23.00 26.94 6.96                                          2        33.6    67.91                                                                                21.28                                                                                26.90                                                                                7.78                                        LOCS    23       23    23    23    23                                          DIFF     0.61   2.68  1.71  0.04   0.82                                        PROB     .453  0.000#                                                                               0.042+                                                                               0.896 0.000#                              ______________________________________                                          * = 10% SIG                                                                    + = 5% SIG                                                                     # = 1% SIG                                                               

                  TABLE 5B                                                         ______________________________________                                         HYBRID SILAGE COMPARISON REPORT                                                VARIETY #1 - 31G20                                                             VARIETY #2 - 3223                                                                           YLD/    MOIST   STR   ADF   CP                                           VAR    TA       %       %     %    %                                           #      ABS      ABS     ABS  ABS    ABS                                 ______________________________________                                         TOTAL SUM                                                                               1       34.31   64.67 23.71 26.99 6.82                                          2       34.24  65.49  27.62                                                                                24.57                                                                                7.41                                        LOCS      25      25    25    25    25                                         DIFF     0.07     0.82                                                                                0.391                                                                                2.43  0.59                                        PROB     .886     0.12                                                                                0.000#                                                                              0.000#                                                                               0.000#                              ______________________________________                                          * = 10% SIG                                                                    + = 5% SIG                                                                     # = 1% SIG                                                               

                  TABLE 5C                                                         ______________________________________                                         HYBRID SILAGE COMPARISON REPORT                                                VARIETY #1 - 31G20                                                              VARIETY #2 - 32K61                                                                         YLD/    MOIST   STR   ADF   CP                                           VAR   TA        %       %     %     %                                          #       ABS     ABS     ABS  ABS   ABS                                  ______________________________________                                         TOTAL SUM                                                                               1       31.69   64.81 23.41 26.79 7.01                                           2      32.10  65.80  24.32                                                                                25.14                                                                                 7.67                                         LOCS   33       33    33    33    33                                           DIFF    0.41    0.99                                                                                 0.91                                                                                 1.65                                                                                 0.65                                         PROB    .414   0.007#                                                                              0.152 0.000#                                                                               0.000#                              ______________________________________                                          * = 10% SIG                                                                    += 5% SIG                                                                      # = 1% SIG                                                               

Further Embodiments of the Invention

This invention includes hybrid maize seed of 31G20 and the hybrid maize plant produced therefrom. The foregoing was set forth by way of example and is not intended to limit the scope of the invention.

As used herein, the term plant includes plant cells, plant protoplasts, plant cell tissue cultures from which maize plants can be regenerated, plant calli, plant clumps, and plant cells that are intact in plants, or parts of plants, such as embryos, pollen, ovules, flowers, kernels, ears, cobs, leaves, seeds, husks, stalks, roots, root tips, anthers, silk and the like.

Duncan, Williams, Zehr, and Widholm, Planta, (1985) 165:322-332 reflects that 97% of the plants cultured which produced callus were capable of plant regeneration. Subsequent experiments with both inbreds and hybrids produced 91% regenerable callus which produced plants. In a further study in 1988, Songstad, Duncan & Widholm in Plant Cell Reports (1988), 7:262-265 reports several media additions which enhance regenerability of callus of two inbred lines. Other published reports also indicated that "nontraditional" tissues are capable of producing somatic embryogenesis and plant regeneration. K. P. Rao, et al., Maize Genetics Cooperation Newsletter, 60:64-65 (1986), refers to somatic embryogenesis from glume callus cultures and B. V. Conger, et al., Plant Cell Reports, 6:345-347 (1987) indicates somatic embryogenesis from the tissue cultures of maize leaf segments. Thus, it is clear from the literature that the state of the art is such that these methods of obtaining plants are, and were, "conventional" in the sense that they are routinely used and have a very high rate of success.

Tissue culture of maize is described in European Patent Application, publication 160,390, incorporated herein by reference. Maize tissue culture procedures are also described in Green and Rhodes, "Plant Regeneration in Tissue Culture of Maize," Maize for Biological Research (Plant Molecular Biology Association, Charlottesville, Va. 1982, at 367-372) and in Duncan, et al., "The Production of Callus Capable of Plant Regeneration from Immature Embryos of Numerous Zea Mays Geneotypes," 165 Planta 322-332 (1985). Thus, another aspect of this invention is to provide cells which upon growth and differentiation produce maize plants having the genotype of 31G20.

Transformation of Maize

With the advent of molecular biological techniques that have allowed the isolation and characterization of genes that encode specific protein products, scientists in the field of plant biology developed a strong interest in engineering the genome of plants to contain and express foreign genes, or additional, or modifed versions of native or endogenous genes (perhaps driven by different promoters) in order to alter the traits of a plant in a specific manner. Such foreign, additional and/or modified genes are referred to herein collectively as "transgenes". Over the last fifteen to twenty years several methods for producing transgenic plants have been developed, and the present invention, in particular embodiments, also relates to transgenic versions of the claimed hybrid maize line 31G20.

Plant transformation involves the construction of an expression vector which will function in plant cells. Such a vector comprises DNA comprising a gene under control of or operatively linked to a regulatory element (for example, a promoter). The expression vector may contain one or more such operably linked gene/regulatory element combinations. The vector(s) may be in the form of a plasmid, and can be used, alone or in combination with other plasmids, to provide transformed maize plants, using transformation methods as described below to incorporate transgenes into the genetic material of the maize plant(s).

Expression Vectors For Maize Transformation Marker Genes

Expression vectors include at least one genetic marker, operably linked to a regulatory element (a promoter, for example) that allows transformed cells containing the marker to be either recovered by negative selection, i.e. inhibiting growth of cells that do not contain the selectable marker gene, or by positive selection, i.e., screening for the product encoded by the genetic marker. Many commonly used selectable marker genes for plant transformation are well known in the transformation arts, and include, for example, genes that code for enzymes that metabolically detoxify a selective chemical agent which may be an antibiotic or a herbicide, or genes that encode an altered target which is insensitive to the inhibitor. A few positive selection methods are also known in the art. One commonly used selectable marker gene for plant transformation is the neomycin phosphotransferase II (nptII) gene, isolated from transposon Tn5, which when placed under the control of plant regulatory signals confers resistance to kanamycin. Fraley et al., Proc. Natl. Acad. Sci. U.S.A., 80: 4803 (1983). Another commonly used selectable marker gene is the hygromycin phosphotransferase gene which confers resistance to the antibiotic hygromycin. Vanden Elzen et al., Plant Mol. Biol., 5: 299 (1985).

Additional selectable marker genes of bacterial origin that confer resistance to antibiotics include gentamycin acetyl transferase, streptomycin phosphotransferase, aminoglycoside-3'-adenyl transferase, the bleomycin resistance determinant. Hayford et al., Plant Physiol. 86: 1216 (1988), Jones et al., Mol. Gen. Genet., 210: 86 (1987), Svab et al., Plant Mol. Biol.. 14: 197 (1990), Hille et al., Plant Mol. Biol. 7: 171 (1986). Other selectable marker genes confer resistance to herbicides such as glyphosate, glufosinate or broxynil. Comai et al., Nature 317: 741-744 (1985), Gordon-Kamm et al., Plant Cell 2: 603-618 (1990) and Stalker et al., Science 242: 419-423 (1988).

Other selectable marker genes for plant transformation are not of bacterial origin. These genes include, for example, mouse dihydrofolate reductase, plant 5-enolpyruvylshikimate-3-phosphate synthase and plant acetolactate synthase. Eichholtz et al., Somatic Cell Mol. Genet. 13: 67 (1987), Shah et al., Science 233: 478 (1986), Charest et al., Plant Cell Rep. 8: 643 (1990).

Another class of marker genes for plant transformation require screening of presumptively transformed plant cells rather than direct genetic selection of transformed cells for resistance to a toxic substance such as an antibiotic. These genes are particularly useful to quantify or visualize the spatial pattern of expression of a gene in specific tissues and are frequently referred to as reporter genes because they can be fused to a gene or gene regulatory sequence for the investigation of gene expression. Commonly used genes for screening presumptively transformed cells include β-glucuronidase (GUS), β-galactosidase, luciferase and chloramphenicol acetyltransferase. Jefferson, R. A., Plant Mol. Biol. Rep. 5: 387 (1987)., Teeri et al., EMBO J. 8: 343 (1989), Koncz et al., Proc. Natl. Acad. Sci. U.S.A. 84:131 (1987), De Block et al., EMBO J. 3: 1681 (1984). Another approach to the identification of relatively rare transformation events has been use of a gene that encodes a dominant constitutive regulator of the Zea mays anthocyanin pigmentation pathway. Ludwig et al., Science 247: 449 (1990).

Recently, in vivo methods for visualizing GUS activity that do not require destruction of plant tissue have been made available. Molecular Probes Publication 2908, Imagene Green™, p.1-4 (1993) and Naleway et al., J. Cell Biol. 115: 151a (1991). However, these in vivo methods for visualizing GUS activity have not proven useful for recovery of transformed cells because of low sensitivity, high fluorescent backgrounds, and limitations associated with the use of luciferase genes as selectable markers.

More recently, a gene encoding Green Fluorescent Protein (GFP) has been utilized as a marker for gene expression in prokaryotic and eukaryotic cells. Chalfie et al., Science 263: 802 (1994). GFP and mutants of GFP may be used as screenable markers.

Promoters

Genes included in expression vectors must be driven by a nucleotide sequence comprising a regulatory element, for example, a promoter. Several types of promoters are now well known in the transformation arts, as are other regulatory elements that can be used alone or in combination with promoters.

As used herein "promoter" includes reference to a region of DNA upstream from the start of transcription and involved in recognition and binding of RNA polymerase and other proteins to initiate transcription. A "plant promoter" is a promoter capable of initiating transcription in plant cells. Examples of promoters under developmental control include promoters that preferentially initiate transcription in certain tissues, such as leaves, roots, seeds, fibers, xylem vessels, tracheids, or sclerenchyma. Such promoters are referred to as "tissue-preferred". Promoters which initiate transcription only in certain tissues are referred to as "tissue-specific". A "cell type" specific promoter primarily drives expression in certain cell types in one or more organs, for example, vascular cells in roots or leaves. An "inducible" promoter is a promoter which is under environmental control. Examples of environmental conditions that may effect transcription by inducible promoters include anaerobic conditions or the presence of light. Tissue-specific, tissue-preferred, cell type specific, and inducible promoters constitute the class of "non-constitutive" promoters. A "constitutive" promoter is a promoter which is active under most environmental conditions.

A. Inducible Promoters

An inducible promoter is operably linked to a gene for expression in maize. Optionally, the inducible promoter is operably linked to a nucleotide sequence encoding a signal sequence which is operably linked to a gene for expression in maize. With an inducible promoter the rate of transcription increases in response to an inducing agent.

Any inducible promoter can be used in the instant invention. See Ward et al. Plant Mol. Biol. 22: 361-366 (1993). Exemplary inducible promoters include, but are not limited to, that from the ACEI system which responds to copper (Mett et al. PNAS 90: 4567-4571 (1993)); In2 gene from maize which responds to benzenesulfonamide herbicide safeners (Hershey et al., Mol. Gen. Genetics 227: 229-237 (1991) and Gatz et al., Mol. Gen. Genetics 243: 32-38 (1994)) or Tet repressor from Tn10 (Gatz et al., Mol. Gen. Genet. 227: 229-237 (1991). A particularly preferred inducible promoter is a promoter that responds to an inducing agent to which plants do not normally respond. An exemplary inducible promoter is the inducible promoter from a steroid hormone gene, the transcriptional activity of which is induced by a glucocorticosteroid hormone. Schena et al., Proc. Natl. Acad. Sci. U.S.A. 88: 0421 (1991).

B. Constitutive Promoters

A constitutive promoter is operably linked to a gene for expression in maize or the constitutive promoter is operably linked to a nucleotide sequence encoding a signal sequence which is operably linked to a gene for expression in maize.

Many different constitutive promoters can be utilized in the instant invention. Exemplary constitutive promoters include, but are not limited to, the promoters from plant viruses such as the 35S promoter from CaMV (Odell et al, Nature 313: 810-812 (1985) and the promoters from such genes as rice actin (McElroy et al., Plant Cell 2: 163-171 (1990)); ubiquitin (Christensen et al., Plant Mol. Biol. 12: 619-632 (1989) and Christensen et al., Plant Mol. Biol. 18: 675-689 (1992)): pEMU (Last et al, Theor. Appl. Genet. 81: 581-588 (1991)); MAS (Velten et al., EMBO J. 3: 2723-2730 (1984)) and maize H3 histone (Lepetit et al., Mol. Gen. Genet. 231: 276-285 (1992) and Atanassova et al., Plant Journal 2(3): 291-300 (1992)).

The ALS promoter, a Xbal/Ncol fragment 5' to the Brassica napus ALS3 structural gene (or a nucleotide sequence that has substantial sequence similarity to said Xbal/Ncol fragment), represents a particularly useful constitutive promoter. See PCT application WO96/30530.

C. Tissue-specific or Tissue-Preferred Promoters

A tissue-specific promoter is operably linked to a gene for expression in maize. Optionally, the tissue-specific promoter is operably linked to a nucleotide sequence encoding a signal sequence which is operably linked to a gene for expression in maize. Plants transformed with a gene of interest operably linked to a tissue-specific promoter produce the protein product of the transgene exclusively, or preferentially, in a specific tissue.

Any tissue-specific or tissue-preferred promoter can be utilized in the instant invention. Exemplary tissue-specific or tissue-preferred promoters include, but are not limited to, a root-preferred promoter,--such as that from the phaseolin gene (Murai et al., Science 23: 476-482 (1983) and Sengupta-Gopalan et al, Proc. Natl. Acad. Sci. U.S.A. 82: 3320-3324 (1985)); a leaf-specific and light-induced promoter such as that from cab or rubisco (Simpson et al., EMBO J. 4(11): 2723-2729 (1985) and Timko et al, Nature 318: 579-582 (1985)); an anther-specific promoter such as that from LAT52 (Twell et al, Mol. Gen. Genet. 217: 240-245 (1989)); a pollen-specific promoter such as that from Zm13 (Guerrero et al., Mol. Gen. Genet. 224: 161-168 (1993)) or a microspore-preferred promoter such as that from apg (Twell et al, Sex. Plant Reprod. 6: 217-224 (1993).

Signal Sequences For Targeting Proteins to Subcellular Compartments

Transport of protein produced by transgenes to a subcellular compartment such as the chloroplast, vacuole, peroxisome, glyoxysome, cell wall or mitochondrion, or for secretion into the apoplast, is accomplished by means of operably linking the nucleotide sequence encoding a signal sequence to the 5' and/or 3' region of a gene encoding the protein of interest. Targeting sequences at the 5' and/or 3' end of the structural gene may determine, during protein synthesis and processing, where the encoded protein is ultimately compartmentalized. The presence of a signal sequence directs a polypeptide to either an intracellular organelle or subcellular compartment or for secretion to the apoplast. Many signal sequences are known in the art. See, for example, Becker et al., Plant Mol. Biol. 20: 49 (1992), Close, P. S., Master's Thesis, Iowa State University (1993), Knox, C., et al., "Structure and Organization of Two Divergent Alpha-Amylase Genes From Barley", Plant Mol. Biol. 9: 3-17 (1987), Lerner et al., Plant Physiol. 91: 124-129 (1989), Fontes et al., Plant Cell 3: 483-496 (1991), Matsuoka et al., Proc. Natl. Acad. Sci. 88: 834 (1991), Gould et al., J. Cell Biol 108: 1657 (1989), Creissen et al., Plant J. 2: 129 (1991), Kalderon, D., Robers, B., Richardson, W., and Smith A., "A short amino acid sequence able to specify nuclear location", Cell 39: 499-509 (1984), Stiefel, V., Ruiz-Avila, L., Raz R., Valles M., Gomez J., Pages M., Martinez-Izquierdo J., Ludevid M., Landale J., Nelson T., and Puigdomenech P., "Expression of a maize cell wall hydroxyproline-rich glycoprotein gene in early leaf and root vascular differentiation", Plant Cell 2: 785-793 (1990).

Foreign Protein Genes and Agronomic Genes

With transgenic plants according to the present invention, a foreign protein can be produced in commercial quantities. Thus, techniques for the selection and propagation of transformed plants, which are well understood in the art, yield a plurality of transgenic plants which are harvested in a conventional manner, and a foreign protein then can be extracted from a tissue of interest or from total biomass. Protein extraction from plant biomass can be accomplished by known methods which are discussed, for example, by Heney and Orr, Anal. Biochem. 114: 92-6 (1981).

According to a preferred embodiment, the transgenic plant provided for commercial production of foreign protein is maize. In another preferred embodiment, the biomass of interest is seed. For the relatively small number of transgenic plants that show higher levels of expression, a genetic map can be generated, primarily via conventional Restriction Fragment Length Polymorphisms (RFLP), Polymerase Chain Reaction (PCR) analysis, and Simple Sequence Repeats (SSR) which identifies the approximate chromosomal location of the integrated DNA molecule. For exemplary methodologies in this regard, see Glick and Thompson, METHODS IN PLANT MOLECULAR BIOLOGY AND BIOTECHNOLOGY 269-284 (CRC Press, Boca Raton,1993). Map information concerning chromosomal location is useful for proprietary protection of a subject transgenic plant. If unauthorized propagation is undertaken and crosses made with other germplasm, the map of the integration region can be compared to similar maps for suspect plants, to determine if the latter have a common parentage with the subject plant. Map comparisons would involve hybridizations, RFLP, PCR, SSR and sequencing, all of which are conventional techniques.

Likewise, by means of the present invention, agronomic genes can be expressed in transformed plants. More particularly, plants can be genetically engineered to express various phenotypes of agronomic interest. Exemplary genes implicated in this regard include, but are not limited to, those categorized below.

1. Genes That Confer Resistance To Pests or Disease And That Encode:

(A) Plant disease resistance genes. Plant defenses are often activated by specific interaction between the product of a disease resistance gene (R) in the plant and the product of a corresponding avirulence (Avr) gene in the pathogen. A plant variety can be transformed with cloned resistance gene to engineer plants that are resistant to specific pathogen strains. See, for example Jones et al., Science 266: 789 (1994) (cloning of the tomato Cf-9 gene for resistance to Cladosporium fulvum); Martin et al., Science 262: 1432 (1993) (tomato Pto gene for resistance to Pseudomonas syringae pv. tomato encodes a protein kinase); Mindrinos et al., Cell 78: 1089 (1994) (Arabidopsis RSP2 gene for resistance to Pseudomonas syringae).

(B) A Bacillus thuringiensis protein, a derivative thereof or a synthetic polypeptide modeled thereon. See, for example, Geiser et al., Gene 48: 109 (1986), who disclose the cloning and nucleotide sequence of a Bt δ-endotoxin gene. Moreover, DNA molecules encoding δ-endotoxin genes can be purchased from American Type Culture Collection (Rockville, Md.), for example, under ATCC Accession Nos. 40098, 67136, 31995 and 31998.

(C) A lectin. See, for example, the disclosure by Van Damme et al., Plant Molec. Biol. 24: 25 (1994), who disclose the nucleotide sequences of several Clivia miniata mannose-binding lectin genes.

(D) A vitamin-binding protein, such as avidin. See PCT application US93/06487 the contents of which are hereby incorporated by. The application teaches the use of avidin and avidin homologues as larvicides against insect pests.

(E) An enzyme inhibitor, for example, a protease inhibitor or an amylase inhibitor. See, for example, Abe et al., J. Biol. Chem. 262: 16793 (1987) (nucleotide sequence of rice cysteine proteinase inhibitor), Huub et al., Plant Molec. Biol. 21: 985 (1993) (nucleotide sequence of cDNA encoding tobacco proteinase inhibitor I), and Sumitani et al., Biosci. Biotech. Biochem. 57: 1243 (1993) (nucleotide sequence of Streptomyces nitrosporeus α-amylase inhibitor).

(F) An insect-specific hormone or pheromone such as an ecdysteroid and juvenile hormone, a variant thereof, a mimetic based thereon, or an antagonist or agonist thereof. See, for example, the disclosure by Hammock et al., Nature 344: 458 (1990), of baculovirus expression of cloned juvenile hormone esterase, an inactivator of juvenile hormone.

(G) An insect-specific peptide or neuropeptide which, upon expression, disrupts the physiology of the affected pest. For example, see the disclosures of Regan, J. Biol. Chem. 269: 9 (1994) (expression cloning yields DNA coding for insect diuretic hormone receptor), and Pratt et al., Biochem. Biophys. Res. Comm.163: 1243 (1989) (an allostatin is identified in Diploptera puntata). See also U.S. Pat. No. 5,266,317 to Tomalski et al., who disclose genes encoding insect-specific, paralytic neurotoxins.

(H) An insect-specific venom produced in nature by a snake, a wasp, etc. For example, see Pang et al., Gene 116: 165 (1992), for disclosure of heterologous expression in plants of a gene coding for a scorpion insectotoxic peptide.

(I) An enzyme responsible for an hyperaccumulation of a monterpene, a sesquiterpene, a steroid, hydroxamic acid, a phenylpropanoid derivative or another non-protein molecule with insecticidal activity.

(J) An enzyme involved in the modification, including the post-translational modification, of a biologically active molecule; for example, a glycolytic enzyme, a proteolytic enzyme, a lipolytic enzyme, a nuclease, a cyclase, a transaminase, an esterase, a hydrolase, a phosphatase, a kinase, a phosphorylase, a polymerase, an elastase, a chitinase and a glucanase, whether natural or synthetic. See PCT application WO 93/02197 in the name of Scott et al., which discloses the nucleotide sequence of a callase gene. DNA molecules which contain chitinase-encoding sequences can be obtained, for example, from the ATCC under Accession Nos. 39637 and 67152. See also Kramer et al., Insect Biochem. Molec. Biol. 3: 691 (1993), who teach the nucleotide sequence of a cDNA encoding tobacco hookworm chitinase, and Kawalleck et al., Plant Molec. Biol. 21: 673 (1993), who provide the nucleotide sequence of the parsley ubi4-2 polyubiquitin gene.

(K) A molecule that stimulates signal transduction. For example, see the disclosure by Botella et al., Plant Molec. Biol. 24: 757 (1994), of nucleotide sequences for mung bean calmodulin cDNA clones, and Griess et al., Plant Physiol. 104: 1467 (1994), who provide the nucleotide sequence of a maize calmodulin cDNA clone.

(L) A hydrophobic moment peptide. See PCT application WO95/16776 (disclosure of peptide derivatives of Tachyplesin which inhibit fungal plant pathogens) and PCT application WO95/18855 (teaches synthetic antimicrobial peptides that confer disease resistance), the respective contents of which are hereby incorporated by reference.

(M) A membrane permease, a channel former or a channel blocker. For example, see the disclosure by Jaynes et al., Plant Sci. 89: 43 (1993), of heterologous expression of a cecropin-β lytic peptide analog to render transgenic tobacco plants resistant to Pseudomonas solanacearum.

(N) A viral-invasive protein or a complex toxin derived therefrom. For example, the accumulation of viral coat proteins in transformed plant cells imparts resistance to viral infection and/or disease development effected by the virus from which the coat protein gene is derived, as well as by related viruses. See Beachy et al., Ann. Rev. Phytopathol. 28: 451 (1990). Coat protein-mediated resistance has been conferred upon transformed plants against alfalfa mosaic virus, cucumber mosaic virus, tobacco streak virus, potato virus X, potato virus Y, tobacco etch virus, tobacco rattle virus and tobacco mosaic virus. Id.

(O) An insect-specific antibody or an immunotoxin derived therefrom. Thus, an antibody targeted to a critical metabolic function in the insect gut would inactivate an affected enzyme, killing the insect. Cf. Taylor et al., Abstract #497, SEVENTH INT'L SYMPOSIUM ON MOLECULAR PLANT-MICROBE INTERACTIONS (Edinburgh, Scotland, 1994) (enzymatic inactivation in transgenic tobacco via production of single-chain antibody fragments).

(P) A virus-specific antibody. See, for example, Tavladoraki et al, Nature 366: 469 (1993), who show that transgenic plants expressing recombinant antibody genes are protected from virus attack.

(Q) A developmental-arrestive protein produced in nature by a pathogen or a parasite. Thus, fungal endo α-1,4-D-polygalacturonases facilitate fungal colonization and plant nutrient release by solubilizing plant cell wall homo-α-1,4-D-galacturonase. See Lamb et al., Bio/Technology 10: 1436 (1992). The cloning and characterization of a gene which encodes a bean endopolygalacturonase-inhibiting protein is described by Toubart et al., Plant J. 2: 367 (1992).

(R) A developmental-arrestive protein produced in nature by a plant. For example, Logemann et al., Bio/Technology 10: 305 (1992), have shown that transgenic plants expressing the barley ribosome-inactivating gene have an increased resistance to fungal disease.

2. Genes That Confer Resistance To A Herbicide, For Example:

(A) A herbicide that inhibits the growing point or meristem, such as an imidazalinone or a sulfonylurea. Exemplary genes in this category code for mutant ALS and AHAS enzyme as described, for example, by Lee et al., EMBO J. 7: 1241 (1988), and Miki et al., Theor. Appl. Genet. 80: 449 (1990), respectively.

(B) Glyphosate (resistance imparted by mutant 5-enolpyruvl-3-phosphikimate synthase (EPSP) and aroA genes, respectively) and other phosphono compounds such as glufosinate (phosphinothricin acetyl transferase (PAT) and Streptomyces hygroscopicus phosphinothricin acetyl transferase (bar) genes), and pyridinoxy or phenoxy proprionic acids and cycloshexones (ACCase inhibitor-encoding genes). See, for example, U.S. Pat. No. 4,940,835 to Shah et al., which discloses the nucleotide sequence of a form of EPSP which can confer glyphosate resistance. A DNA molecule encoding a mutant aroA gene can be obtained under ATCC accession No. 39256, and the nucleotide sequence of the mutant gene is disclosed in U.S. Pat. No. 4,769,061 to Comai. European patent application No. 0 333 033 to Kumada et al. and U.S. Pat. No. 4,975,374 to Goodman et al. disclose nucleotide sequences of glutamine synthetase genes which confer resistance to herbicides such as L-phosphinothricin. The nucleotide sequence of a phosphinothricin-acetyl-transferase gene is provided in European application No. 0 242 246 to Leemans et al. De Greef et al., Bio/Technology 7: 61 (1989), describe the production of transgenic plants that express chimeric bar genes coding for phosphinothricin acetyl transferase activity. Exemplary of genes conferring resistance to phenoxy proprionic acids and cycloshexones, such as sethoxydim and haloxyfop, are the Acc1-S1, Acc1-S2 and Acc1-S3 genes described by Marshall et al., Theor. Appl. Genet 83: 435 (1992).

(C) A herbicide that inhibits photosynthesis, such as a triazine (psbA and gs+ genes) and a benzonitrile (nitrilase gene). Przibilla et al., Plant Cell 3: 169 (1991), describe the transformation of Chlamydomonas with plasmids encoding mutant psbA genes. Nucleotide sequences for nitrilase genes are disclosed in U.S. Pat. No. 4,810,648 to Stalker, and DNA molecules containing these genes are available under ATCC Accession Nos. 53435, 67441 and 67442. Cloning and expression of DNA coding for a glutathione S-transferase is described by Hayes et al., Biochem. J. 285: 173 (1992).

3. Genes That Confer Or Contribute To A Value-Added Trait, Such As:

(A) Modified fatty acid metabolism, for example, by transforming a plant with an antisense gene of stearoyl-ACP desaturase to increase stearic acid content of the plant. See Knultzon et al., Proc. Natl. Acad. Sci. U.S.A. 89: 2624 (1992).

(B) Decreased phytate content

(1) Introduction of a phytase-encoding gene would enhance breakdown of phytate, adding more free phosphate to the transformed plant. For example, see Van Hartingsveldt et al., Gene 127: 87 (1993), for a disclosure of the nucleotide sequence of an Aspergillus niger phytase gene.

(2) A gene could be introduced that reduces phytate content. In maize, this, for example, could be accomplished, by cloning and then reintroducing DNA associated with the single allele which is responsible for maize mutants characterized by low levels of phytic acid. See Raboy et al., Maydica 35: 383 (1990).

(C) Modified carbohydrate composition effected, for example, by transforming plants with a gene coding for an enzyme that alters the branching pattern of starch. See Shiroza et al., J. Bacteriol. 170: 810 (1988) (nucleotide sequence of Streptococcus mutans fructosyltransferase gene), Steinmetz et al., Mol. Gen. Genet. 200: 220 (1985) (nucleotide sequence of Bacillus subtilis levansucrase gene), Pen et al., Bio/Technology 10: 292 (1992) (production of transgenic plants that express Bacillus licheniformis α-amylase), Elliot et al., Plant Molec. Biol. 21: 515 (1993) (nucleotide sequences of tomato invertase genes), S.o slashed.gaard et al., J. Biol. Chem. 268: 22480 (1993) (site-directed mutagenesis of barley α-amylase gene), and Fisher et al., Plant Physiol. 102: 1045 (1993) (maize endosperm starch branching enzyme II).

Methods for Maize Transformation

Numerous methods for plant transformation have been developed, including biological and physical, plant transformation protocols. See, for example, Miki et al., "Procedures for Introducing Foreign DNA into Plants" in Methods in Plant Molecular Biology and Biotechnology, Glick, B. R. and Thompson, J. E. Eds. (CRC Press, Inc., Boca Raton, 1993) pages 67-88. In addition, expression vectors and in vitro culture methods for plant cell or tissue transformation and regeneration of plants are available. See, for example, Gruber et al., "Vectors for Plant Transformation" in Methods in Plant Molecular Biology and Biotechnology, Glick, B. R. and Thompson, J. E. Eds. (CRC Press, Inc., Boca Raton, 1993) pages 89-119.

A. Agrobacterium-mediated Transformation

One method for introducing an expression vector into plants is based on the natural transformation system of Agrobacterium. See, for example, Horsch et al., Science 227: 1229 (1985). A. tumefaciens and A. rhizogenes are plant pathogenic soil bacteria which genetically transform plant cells. The Ti and Ri plasmids of A. tumefaciens and A. rhizogenes, respectively, carry genes responsible for genetic transformation of the plant. See, for example, Kado, C. I., Crit. Rev. Plant. Sci. 10: 1 (1991). Descriptions of Agrobacterium vector systems and methods for Agrobacterium-mediated gene transfer are provided by Gruber et al., supra, Miki et al., supra, and Moloney et al., Plant Cell Reports 8: 238 (1989). See also, U.S. Pat. No. 5,591,616, issued Jan. 7, 1997.

B. Direct Gene Transfer

Despite the fact the host range for Agrobacterium-mediated transformation is broad, some major cereal crop species and gymnosperms have generally been recalcitrant to this mode of gene transfer, even though some success has recently been achieved in rice and maize. Hiei et al., The Plant Journal 6: 271-282 (1994); U.S. Pat. No. 5,591,616, issued Jan. 7, 1997. Several methods of plant transformation, collectively referred to as direct gene transfer, have been developed as an alternative to Agrobacterium-mediated transformation.

A generally applicable method of plant transformation is microprojectile-mediated transformation wherein DNA is carried on the surface of microprojectiles measuring 1 to 4 μm. The expression vector is introduced into plant tissues with a biolistic device that accelerates the microprojectiles to speeds of 300 to 600 m/s which is sufficient to penetrate plant cell walls and membranes. Sanford et al., Part. Sci. Technol. 5: 27 (1987), Sanford, J. C., Trends Biotech. 6: 299 (1988), Klein et al., Bio/Technology 6: 559-563 (1988), Sanford, J. C., Physiol Plant 79: 206 (1990), Klein et al., Biotechnology 10: 268 (1992). In maize, several target tissues can be bombarded with DNA-coated microprojectiles in order to produce transgenic plants, including, for example, callus (Type I or Type II), immature embryos, and meristematic tissue.

Another method for physical delivery of DNA to plants is sonication of target cells. Zhang et al., Bio/Technology 9: 996 (1991). Alternatively, liposome or spheroplast fusion have been used to introduce expression vectors into plants. Deshayes et al., EMBO J., 4: 2731 (1985), Christou et al., Proc Natl. Acad. Sci. U.S.A. 84: 3962 (1987). Direct uptake of DNA into protoplasts using CaCl2 precipitation, polyvinyl alcohol or poly-L-ornithine have also been reported. Hain et al., Mol. Gen. Genet. 199: 161 (1985) and Draper et al., Plant Cell Physiol. 23: 451 (1982). Electroporation of protoplasts and whole cells and tissues have also been described. Donn et al., In Abstracts of VIIth International Congress on Plant Cell and Tissue Culture IAPTC, A2-38, p 53 (1990); D'Halluin et al., Plant Cell 4: 1495-1505 (1992) and Spencer et al., Plant Mol. Biol. 24: 51-61 (1994).

Following transformation of maize target tissues, expression of the above-described selectable marker genes allows for preferential selection of transformed cells, tissues and/or plants, using regeneration and selection methods now well known in the art.

The foregoing methods for transformation would typically be used for producing transgenic inbred lines. Transgenic inbred lines could then be crossed, with another (non-transformed or transformed) inbred line, in order to produce a transgenic hybrid maize plant. Alternatively, a genetic trait which has been engineered into a particular maize line using the foregoing transformation techniques could be moved into another line using traditional backcrossing techniques that are well known in the plant breeding arts. For example, a backcrossing approach could be used to move an engineered trait from a public, non-elite line into an elite line, or from a hybrid maize plant containing a foreign gene in its genome into a line or lines which do not contain that gene. As used herein, "crossing" can refer to a simple X by Y cross, or the process of backcrossing, depending on the context.

Industrial Applicability

Maize is used as human food, livestock feed, and as raw material in industry. The food uses of maize, in addition to human consumption of maize kernels, include both products of dry- and wet-milling industries.

Maize, including both grain and non-grain portions of the plant, is also used extensively as livestock feed, primarily for beef cattle, dairy cattle, hogs, and poultry.

Industrial uses of maize include production of ethanol, maize starch in the wet-milling industry and maize flour in the dry-milling industry. The industrial applications of maize starch and flour are based on functional properties, such as viscosity, film formation, adhesive properties, and ability to suspend particles. The maize starch and flour have application in the paper and textile industries. Other industrial uses include applications in adhesives, building materials, foundry binders, laundry starches, explosives, oil-well muds, and other mining applications.

Plant parts other than the grain of maize are also used in industry. Stalks and husks are made into paper and wallboard and cobs are used for fuel and to make charcoal.

The seed of the hybrid maize plant and various parts of the hybrid maize plant and transgenic versions of the foregoing, can be utilized for human food, livestock feed, and as a raw material in industry.

Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity and understanding, it will be obvious that certain changes and modifications may be practiced within the scope of the invention, as limited only by the scope of the appended claims.

DEPOSITS

A deposit of the seed of hybrid 31G20 is and has been maintained by Pioneer Hi-Bred International, Inc., 700 Capital Square, 400 Locust Street, Des Moines, Iowa 50309-2340, since prior to the filing date of this application. Access to this deposit will be available during the pendency of the application to the Commissioner of Patents and Trademarks and person determined by the Commissioner to be entitled thereto upon request. Upon allowance of any claims in the application, the Applicant(s) will make available to the public without restriction a deposit of at least 2500 seeds of hybrid 31G20 with the American Type Culture Collection (ATCC), 10801 University Boulevard, Manassas, Va. 20110-2209. The seeds deposited with the ATCC will be taken from the same deposit maintained at Pioneer Hi-Bred and described above. Additionally, Applicant(s) will meet all the requirements of 37 C.F.R. §1.801-1.809, including providing an indication of the viability of the sample when the deposit is made. This deposit of Hybrid Maize Line 31G20 will be maintained without restriction in the ATCC Depository, which is a public depository, for a period of 30 years, or 5 years after the most recent request, or for the enforceable life of the patent, whichever is longer, and will be replaced if it ever becomes nonviable during that period. 

What is claimed is:
 1. Hybrid maize seed designated 31G20, representative seed of said hybrid 31G20 having been deposited under ATCC accession number.
 2. A maize plant, or its parts, produced by the seed of claim
 1. 3. Pollen of the plant of claim
 2. 4. An ovule of the plant of claim
 2. 5. A tissue culture of regenerable cells of a hybrid maize plant 31G20, representative seed of said hybrid maize plant 31G20 having been deposited under ATCC accession number , wherein the tissue regenerates plants capable of expressing all the morphological and physiological characteristics of said hybrid maize plant 31G20.
 6. A tissue culture according to claim 5, the cells or protoplasts being from a tissue selected from the group consisting of leaves, pollen, embryos, roots, root tips, anthers, silks, flowers, kernels, ears, cobs, husks, and stalks.
 7. A maize plant, or its parts, regenerated from the tissue culture of claim 5 and capable of expressing all the morphological and physiological characteristics of hybrid maize plant 31G20, representative seed having been deposited under ATCC accession number.
 8. A hybrid maize plant according to claim 2, wherein the genetic material of said plant contains one or more transgenes.
 9. A maize plant, or its parts, wherein at least one ancestor of said maize plant is the maize plant, or its parts, of claim 2, said maize plant expressing a combination of at least two 31G20 traits selected from the group consisting of: a relative maturity of approximately 119 based on the Comparative Relative Maturity Rating System for harvest moisture of grain, excellent, stable grain yield, strong stalks, good resistance to Northern Leaf Blight, excellent stay green, above average early growth, excellent husk cover, very good resistance to Gray Leaf Spot, very good resistance to Southern Leaf Blight, very good resistance to Northern Leaf Blight, good test weight, adapted to no-till environments, and well suited to the Southcentral and Southeast regions of the United States.
 10. A method for developing a maize plant in a maize plant breeding program using plant breeding techniques, which include employing a maize plant, or its parts, as a source of plant breeding material, comprising: obtaining the maize plant, or its parts, of claim 2 as a source of said breeding material.
 11. The maize plant breeding program of claim 10 wherein plant breeding techniques are selected from the group consisting of: recurrent selection, backcrossing, pedigree breeding, restriction fragment length polymorphism enhanced selection, genetic marker enhanced selection, and transformation.
 12. A method for developing a maize plant in a maize plant breeding program using plant breeding techniques, which include employing a maize plant, or its parts, as a source of plant breeding material, comprising: obtaining the maize plant, or its parts, of claim 8 as a source of said breeding material.
 13. The maize plant breeding program of claim 12 wherein plant breeding techniques are selected from the group consisting of: recurrent selection, backcrossing, pedigree breeding, restriction fragment length polymorphism enhanced selection, genetic marker enhanced selection, and transformation. 